First of all, Brightside or any 2-part polyurethane paint like Awlgrip (Brightside is one part), will blister when submerged and exposed to water for long periods of time. You (the person who started this thread) want to paint from gunwale to waterline (which is called the topsides), so you shouldn't have a blistering problem unless you have the waterline not in the right place, where it is submerged. If you use antifouling paint, that paint should be a bit above where the boat floats on her lines.
Preparation is always the best way to get final results. That means cleaning the surface well so there are no contaminants, and the solvent you used shouldn't leave any contaminants either. Then a good sanding, so you get a frosty finish with no shininess showing through. A good sanding gives you the proper tooth for the paint. A shiny surface has no lasting tooth - so sand well. Then clean again.
Primer has a few purposes. One is to help bond the final coat choice to the surface you are painting and the second is it helps fill up porosity which is often evident especially on older fiberglass. Dark or gray primers are used for reds, dark blues, dark greens, black, etc. while white primers are used for lighter colors. After priming, sanding and cleaning is done again. It is always a good idea to use primers designed by the manufacturer for the paint you will finish with.
When cleaning, paper towels are good (some shop towels have chemicals in them. Don't use them) Certainly not any cloths that leave anything behind. Keep changing the towels, rotating often, instead of pushing sanding dust, oils, waxes, etc. around and around. You want to eliminate these things rather than push them around. Solvents that don't flash too quickly, such as acetone, are not good choices. Something with a degreaser dewaxer is preferred. Since you are using an interlux product, Interlux Fiberglass Solvent Wash is a good choice.
Application of the top coat can be sprayed or rolled or brushed on. There are different thinners for each method. Brushing thinners will help the flow of the paint if rolling or brushing. Part of the reason for use of different solvents beside viscosity is the evaporation drying time, which varies between the two methods.
It is always better to apply more than one thin coat, rather than fewer thick coats.
When applying, create a "wet edge" throughout the whole process so it all dries consistently. Don't paint 1/4 of your hull, go have a up of coffee and then return after a bit and start where you left off. That would be disastrous .
If you are rolling and tipping, then have help on hand. One person to roll and another to tip.
Proper preparation certainly is huge to get fabulous results. I've seen paint jobs that are rolled and tipped look as good as a spray job.
Good luck, and be patient and diligent.
