> If it is space or toy the area or toy is removed immediately from the dog so that objection have the opposite result to that wanted - in other words the growl leads to loss of the desired object.
This is an extremely risky strategy for most people to follow because it tends to result in escalation of the problem - and such situations as you describe which require the use of protective clothing. No dog should be put in a position where it is feeling so threatened that such clothing is needed - if the guarding is that bad, then all access to guardable things or spaces should be restricted to prevent it happening to begin with, and the problem worked on initially in controlled setups. The dog guards an item or space because it thinks it is going to lose that space, taking the item or space away just confirms to the dog that this is going to happen so they up their efforts next time. I've had many people find exactly that response when they take an item away - Linc guarded the sofa ever so slightly from his last owner when first asked verbally to move, the owner then tried to actually remove him and nearly got bitten for his efforts.
I have people do swaps with higher value items, in controlled circumstances - so starting with giving the dog something low value that they won't guard, then swapping that for something slightly better, gradually increasing the value of both things. So as has been said, the dog learns that the owner will always have something better. If it's done thoroughly, the dog will give up something higher value in anticipation of something better, even if you've only got mediocre treats.
Space guarding in the dogs I've had with that problem has been a trust issue, so I work on teaching the dogs that I will heed any warnings they give - that actually lowers the warning responses because they relax and learn to trust me, and trust that I won't just ignore them and carry on making them uncomfortable. I teach movement cues (pointing a direction to walk in, an 'off' cue, 'out' for leaving the room) outside of a guarding situation so that if such a situation does arise, I can move the dog calmly and without confrontation.