The u-40 product you dscribe works fine but it STINKS something fierce, at least to my nose. Satin varnishes will work fine, you will need 2 -3 coats over a color preserved wrap, use interior not the exterior that is often reccomended. Don't forget to stir thoroughly before use or it won't be satin, they use fine mica(I think) dust in it to make the finish unglossy(is that a word?). The interior dries much faster and harder and has more than enough flexibility for guide wraps on a graphite blank.
splinter