Yes, that seems to have worked for us too.
Iv done both and I think some things can be rewarded with food, others toys, praise and some things should be a given. A 'this is what I expect and no less' if that makes sense.

I would probably start by make that dog earn every bit of its food. The dog would have to learn the food is mine and I'm kind enough to give you some in exchange for what I want - call that bribary if you like, but I would do that and eventually work up to it being a bit in a bowl (that I was holding), not all from my hand and so on. making it good for food to come from your hands and food to go from your hand into the bowl.
and teaching a good solid leave too

I've also taken on resource guarders and trained them there really is no need to guard anything from me or each other for that matter. When Milan first arrived she'd had a cr@p start in life and had been living on the streets fending for herself so with that in mind and also needing to avoid scuffles with the other dogs, I started off by not taking anything away from her, she had to learn that my hands in her bowl was not an issue, so I started her off with very little food and added to her bowl rather than taking away. Treats were plentiful and they had to all work for them, there was never a need to fight for them because if she missed one when tossed towards her there were always plenty more. I also made a game out of her trying to get the treat out of my hand just using ah ah if she got a bit rough and when she was gentle she was rewarded with a fuss. She picked up "Leave it" the first full day she was here, not just on her own but surrounded by the others doing a group leave too. Just because we expect our dogs to follow commands it doesn't mean we are rough or use force on the dogs, that's no way to get results, although I am very tactile and hands on with them.

Mine have seemed to see leave that thing on the ground/table/chair/wherever as being completely different to leave that thing you've got hold of. They have all been fine with leaving food on the floor if told to but once they've got it in their mouth it's another matter.

Teaching a 'give' or 'drop it' will help, then you can tell them to leave it once they have.

Which is what I use swaps for. I was just wondering how people who won't use swaps teach it. The way we were taught with Shadow was to force his jaws open and take it. Needless to say, it didn't go down very well....

I honestly can't think of any other ways to teach it Well, there's the choke them until they have no choice but to open their mouth way but I found that barbaric

I would say practice is the answer, don't wait until they have something you need to get back off of them but practice on things that really are not that important. I would start with "Give" and when they give it up I praise them and give it back and repeat, then intersperse with a couple of other commands and then back to "Give" always ending before they get fed up with it. Once they're fine with that move on to something more valuable and so on.

EH!

No swaps and treats can be used to teach 'give' but once a behaviour is learned and reinforced, they know whats expected, you can just praise and/or play.

Give, I think I did give a treat actually until he knew what it meant. (you can teach 'trade' seperate if you wish) After that he knew exactly what 'give' meant so I didnt have to teach the behaviour/trade anything, just expected him to do it and just praised him doing the right thing. Some dogs can learn with praise alone or a 'special toy'

When using treats instead of always luring (apart from trick training) I also taught that a wrong decision can mean I remove a treat/praise or toy - allowing them to think (and think they chose to do it - just like men really - make them think its their decision LOL joke btw) so if they didnt do it I say 'a-a' (as I visibly put treat in pocket/walk away/put toy in pocket) and then he would usually decide that he didnt want to lose the treat/reward so do the right thing, then get reward. Once they know what something is and what is expected (i.e. house rules) you shouldnt really need to keep rewarding. Praise can do.

Tennis balls can be a good way to teach if they arent possesive of them, throw one, show another one, when they come and drop the other one you say 'drop' or 'give' and throw the next one. All depends on the dog you have as to whats best probably. As long as the dog is really conditioned to think 'give' is a great thing with great reward then once that connection is there you can use it with a lot.

Later on though, when they know what things mean, they have no reason not to 'obey' so I just sort of expect them to do it - I think its important for your attitude to show that you mean it, be confident, use tone etc.

Also, as Trouble says, practice makes perfect. Short little sessions of a couple of mins a few times a day, always end on a positive.

Some interesting replies

Tyler loves his ball and will give that up no problem to all the kids,we did reward based training when he was a pup and gradually went down to commands only with out the treats.

perhaps he is picking up that your son is a little nervous of dogs, or his voice wasnt controlled enough?

I think my worry would be that he knows fine to give (he does it for you) but feels he can 'challenge' or 'deny' your son.

Do you still practice his commands on a regular basis or just when needed Sal?
With us having so many and fosters in and out on a regular basis we really do have to practice constantly although it's built into everything we do. I've just had 6 dogs in the kitchen and put one saucepan to be licked on the floor, as I put it down I said "leave it" and they all promptly left it and sat down trying to will it towards them, I then let them have a go at cleaning it out one at a time by telling them which one could lick it, while the others were hand fed a bit of pasta each and they could only take it even when wafted under their noses once I said their name, for me it's the only way to keep order and otherwise Diesel would have everything cos he's fastest