Dolph26,
I use a coat of acraglass Painted on with a brush. Just mix it without the glass floc, and spread it out in a shallow flat container. It will take longer to setup because the chemical reaction is faster when it is allowed to generate heat.
If you glassed the stock and it still changes POI. You've either not relieved the stock enough, or didn't make the glass thick enough to remain ridged. If I'm going to the trouble to glass the stock, I don't scrimp on the glassbedding. I buy the shop kits that include a Qt of resin and always mix more than what's needed