I do use a spray bottle filled with a mix of water and a tiny bit of handwashing detergent (like Woolight, but the Dollar store version but you can use any laundry detergent that has phosphorous, about two capfuls for a tiny 10 oz bottle and top off with water). Just mist it on under black light if it needs a refresher. Mostly I like doing it because it's fun seeing the water glow as I'm applying, but it definitely doesn't hurt to refresh.