I learned hard way never paint worn concrete pools with pool epoxy.
Claimed high solids lasts years ect well..
10 gallons, $1000, wow how great it is! I told everyone. Dirt,green stuff, everything just slid right off so nice.
1 year later, chalk galore, clog filter every time i vacuum, was mistake.
Pool guy had to torch it till it popped off entire pool (extra $1000) added to resurface with diamond brite.
Aluminum wheelchair ramp in pool also was painted, stripped & epoxied with best marine bottom epoxy..same story.
Painted ramp again 2yrs ago with rustolium industrial epoxy, same story. Need to redo ramp in stainless.
Never epoxy pool. Top cap you're looking to do would probably be good 2 yrs. Single stage good idea.