the minwax sanding sealer should work as well of course it doesnt hurt try a sample first, but I cant imagine minwax sanding sealer not working with minwax poly.

Where I live you cant get sanding sealer, I ended up using a spray can of transparent varnish that is used generally over outdoor furniture and such. It work great.

air-madness how do you use the wbpoly to seal the grain without warping the wood? I have heard of doing that but it made me a little nervous.. if that sheeting warps you are in a heap of trouble!