I haven’t used any pre made aerosol products myself.
Air inhibits gelcoat from curing. You can apply several coats of unwaxed gelcoat over each other and spray a PVA mold release liquid over the gelcoat to cure it by blocking the air from the surface. Waxed or finish gelcoat cures by having the wax rise to the surface as it cures to block the air contact.
If you have a small repair you can sand the area, wipe it with acetone to clear out any wax or debris and mix up a small batch of bondo to fill the basic repair. After it cures(20 minutes), sand it smoothe and mix up a small batch of waxed gelcoat with 10-12 drops of catalyst per ounce. I use a bondo spreader or an old credit card to apply and smooth the gelcoat, sanding with 220 and then 400 grit when cured.
If you want to spray it on, you can use a Preval project sprayer to apply the gelcoat. I usually mix 2 oz of gelcoat, mix in the catalyst and then thin it about 10-15 % with acetone before putting it into the spray bottle. I spray in a small circular motion to build up the material as it comes out in a spatter fashion. Gelcoat doesn’t really sag or run much so you can spray it on thick and it will be ok. If you are careful spraying and don’t overload the repair site, it won’t take much effort to sand it smooth and polish it up.