yes you can seal the belly every time you work on it,, spray on something or just glue is fine,,
it is proabably alot drier where you are working on the bow,, can you put it someplace with no heat when you are finished working on it,, if you coat it every time you wont get any more checks, as stated, they are not hurting anything,, but I dont like them either if I can avoid them,,
and Pat I do agree with you about the moisture, I just think a thin coat of something lets the moisture come out a bit slower,, and lets the wood acclimate to the climate without checking so much,, or that is my experience,, i have done that quite a bit on sinew bows ,, with postive results,, ,, seems like the sinew puts quite a bit of moisture back in the bow,, and if it comes out the belly it will check,, the glue on the belly seems to force it to come out the back,,