do you think taking very small pinches for a while and gradually increasing the size will resensitize my  nose

nope big pinches are easier. Small punches are more likely to irritate the nose.

I find small pinches best for tasting new snuffs, especially mentholated ones. Well, lots of small pinches!

My pinch size varies according to the grind. For me, the finer the grind, the smaller the pinch. I have tried taking larger pinches of the finer snuffs, but quite frankly I might as well just squirt pepper spray in my face. If you are desensitised to scent, stick with something plain for a while. Some snuffs “wake up” with a little warming, or a little rehydration if they’ve dried out a bit.