fairing / filler compound

[lbhsbz]

I got the new transom wood core bonded in with West Systems 404, now trying to fill the gaps around the edges and make filets so I can tab everything in. I'm using WS Epoxy. I have some 407 low density filler than I've been attempting to use, but it seems that there becomes a point where it just doesn't get any thicker...and still runs out by the time it starts to kick. I'm getting pissed off.
Is there some pre-mixed stuff I should be using? Do I have to add some milled fibers? Any advice?

[XstreamVking]

Cab-o-sil AKA... (fumed silica) is the stuff you need. A peanut butter type mix will stay in place and not drain. The micro ballons (lo density filler ) you are using does not absorb the resin completely and have spaces in between them. So you get the drain.