To color match and blend the gelcoat to the existing hull I used a 1.8mm gravity fed spray gun with a 20oz hopper. Temperatures were in the mid-50's so I warmed the gelcoat and spray gun to about 72 degrees. As things cooled off very quickly I also thinned the gelcoat with 8% acetone by volume and 2% MEKP (catlyst) by volume. The cold temps acted fast and the flow rate was very low. As usual I used 40PSI (open trigger) on the spray gun. The gelcoat layed down pretty smooth with a light orange peel texture which was easily sanded smooth with 400 grit and progressively finer papers. In warmer weather I would use less acetone.
For the non-skid I used gelcoat thickened with cabosil and with the temps in the 50's had no problem getting the gel to "peak up" creating a nice non-skid surface. I've used non-waxed gelcoat to ensure good bonds with over coating. To cure gelcoat you need an absence of air so PVA (Poly Vinyl Alc0hol) air barrier thinned with some water and applied with a spray bottle to block out the air for a tack free cure.