: Just tried using some cab-o-sil to keep epoxy from getting runs in it on the
: final fill coat. I mixed the epoxy first, then added a about 1/12 by
: volume of the fused silica and several things happend: 1st, the epoxy
: mixture in the cup got a lot of air bubbles in it, which is what I allways
: try to avoid.

I don't recommend the cab-o-sil to thicken the epoxy. Like Lee said, it will dull the finish and make sanding more difficult.

Instead, use the same brushing pattern I use for varnish. Working from centerline to sheer line in about 1 foot wide sections: With a full brush spread on the epoxy using horizontal strokes (parallel to the centerline). Without refilling the brush, even it out with vertical strokes (center to sheer line). Then one more time with a lighter touch tip it off with horizontal strokes. Move on the next section. (If I were varnishing, I would alternate sides to maintain a wet edge.)

The key to avoiding drips and sags is getting the coat even and smooth. If you are careful you can actually end up applying quite a bit of resin in one coat.