Re: mixing primer and top coat
One thing I do know... Interlux paints are awesome. I totally repainted my 24' Sea Ray about 5 years ago with fabulous results. I followed their instructions to a "T" and never had a lick of problems.
I used a foam roller and an expensive paint brush where the roller wouldn't go and around the tight spots under the rub rail etc. I did two coats of primer sanded in between each coat then a light sand on the first finish coat. Last/finish coat was like glass; looked like it was sprayed on when done. I used one quart of paint, one of primer. Still had some left for touch ups. You'll find touch up is simple too, just a little sand paper and paint. It looks great and blends in real well.
If they say use 50/50 primer and top coat for second app, do it. Questions? See the web site for answers.