Thanks Woe, It was quite a job. It took way more hours than I care to admit. Most of that was spent grinding and sanding. It's all in the prep.
So, my idea was to try and match the consistency of joint compound using the fumed silica and gelcoat. The silica would not only help to make larger droplets from the texture gun, but also increase the strength and durability of the finished texture. It really was a trial and error to get the consistency correct. I think I ended up close to 100% by volume of silica and gelcoat, so close to a 50/50 mix by volume. Of course, when mixed together, the total volume doesn't increase very much due to the very low density of the fumed silica. The viscosity changes quite a bit though.
Because of the relatively small volumes of material (gelcoat, fumed silica mix), I used a plastic bag to hold and help feed the mixture when spraying. To explain: I used plastic bags that are designed to act as a liner for the dump gun cup. Basically just a deep, narrow, and fairly heavy duty plastic bag. I placed the bag in a quart cup and added the mixture. I then fed the top of the bag through the hopper of the texture gun, squeezed out the air, and attached the gun portion to the hopper with the bag end folded back. This accomplished three things. First, it allowed me to squeeze the bag while spraying to get the mixture into the gun, second, it allowed for much easier clean-up because the hopper stayed mostly clean, and I could throw away the bag, and third it made for less wasted material.
Spraying was the same as texturing drywall, get the coverage that you want, and keep the gun moving. After spraying the texture, I sprayed a light coat of PVA to allow for the gelcoat mixture to cure. After it was cured, I used a wet sander and 320 or 400 grit sandpaper to smooth down the peaks and level out the texture. Simple.
