Personally, I wouldn't apply fiberglass coatings because I don’t want to inhale the chemicals while applying. Methyl Ethyl Ketone, or MEK (no Bueno) is the catalyst that creates isophthalic resins. It is probably safe to roll epoxy. You should be aware of possible fumes or gases when coatings are applied in unventilated areas.
Although most people hire professionals to help with this task, some will attempt it on their own. Although this is a complex task, it is possible if you have all the necessary tools, knowledge, and time.
A thermoplastic polymer powder coat such as ecoFINISH will protect and seal fiberglass. Covering a small to moderate-sized pool typically costs between $10,000 and $14,000. Although it's a more expensive option, this type of finish is also very resistant to weather changes, harsh chemicals, extreme temperature changes, and other factors.
aggregate pool finish