quite often , pending the age of the unit your restoring , the solvents in whatever finish your applying can disturb the glue underneath the veneer.

your best bet is to strip it back raw , make sure you wash off the stripper well (neutralise it with water or thinners) , sand it with 180-220.

use a 2pack (poly) sealer , sand that with 400 , then apply your topcoat.

it is much better to spray the product rather than brushing , but if u do brush , use a very fine haired/bristled brush and make the first coat light.

i am a furniture polisher by trade , allthough i have only done a little of the older techniques of french polishing.