I have used both Interlux and gel coat, and I recommend gel coat any day over the other and its equivalents. Yes you can brush Interlux on and you will "eventually" get good at tipping it out and making sure it does not blush. Yes Interlux is hard as a rock but that is its draw back. It does and will stratch. When it does you will not be able to buff it out. Sanding it is exhuasting and requires repainting. Further, if you have contured areas better have a good hand because you have only one shot or get out the mega sander. Lastly, it is dangerous to spray without a positive ventilator.

Whereas, gel coat is designed to be sanded and buffed. It is softer. It is forgiving and easy to repair. Sanding and buffing out a new coat is rewarding and therapuetic. Shooting gel coat is not hard and will not kill you like Interlux can. Get over the mystic of using a spayer and go for the gel.

Good Luck