Yes, @Johano, you need to dry them before regrinding. And you really won’t loose neither flavour nor nicotine, just don’t use high temperatures. 40-50 C is safe. You’ll mix it with the rest then.
@Gunnar, indeed, schmalzlers and some other medium-coarse snuffs are easy to break down. I usually use the back end of my snuff spoon, when loading boxcar. When it comes to rappee (very moist snuff), those balls can be a headache, similar to loose snus balls… Sticky mess.
I assume, in a way it’s similar process to that of rolling/making a snow ball. If you shake the tin with reground snuff vigorously long enough, some balls will form again. By the way, it’s not a problem with snus; on the contrary, you always find some naturally pre-rolled bolus in pocket-carried can, often hard enough for lip. Really handy :). Loose snus moisture is around 50%, fresh rappee is close to that (if not the same). I’ll definitely try it in the lip next time I procure some.