Thermoplastic polymer powder coatings such as ecoFINISH, can be used to seal and protect fiberglass. To cover a small- to medium-sized pool, it will cost approximately $10,000 to $14,000. Although this finish can be costly, it is durable and resistant to extreme temperatures, chemicals, weather, and harsh weather conditions.
Concrete pools are not as durable as other types and require replastering quite often. Resurfacing concrete pools is usually more expensive than other styles. It typically costs around $10,000. The same finishes can also be used to maintain the pool's appearance, safety, and seal.
I personally wouldn’t apply a fiberglass coating because I don’t want to breathe the stuff when applying. The catalyst for isophthalic resins is Methyl Ethyl Ketone (MEK) – no Bueno! You are probably okay rolling on an epoxy. Just beware of fumes or gases when applying coatings in unventilated areas.