dstarr
Try shellac.
That is my suggestion as well.
There are several brands, Kilz, B-I-N, Bulls Eye. The pigment will help fill voids in the grain and it is easily sandable after drying.
Mod-Podge? I'm not sure if the sanding qualities of this would be very good. I think it is a PVA based adhesive, like Elmer's glue, and may not take paint too well either.
I could be wrong on that.
Good Luck, Ed
