[mcaswell]

I've just done a few trials with our epoxy FASTSTEEL. This material comes in a 'tootsie roll' bar, that you just cut off the amount required. Roll it in you hands to mix it, then place it onto a roughed up/bead blasted surface, and press in firmly.

To shape the material, simply press with a wet finger (spit is good!) and work the material in to smooth it out.
Sometimes lacquer thinner will also help smooth it out.

Faststeel can be sanded or ground, but it is very tough, not like Bondo.

If you do a good job of placing the material, you can powder coat it while it is still soft.
The 400 deg temps will rapidly cure the resin, and this 'post cure' will actually enhance its strength by some 20% or more.