defiantly use a lot of fresh clean water to rinse with or it will digg the dirt in the sanded pain as you work
i havent had any luck with wet sanding paint unless it was cured! it gums up the paper ,and splotches the paint
use water on the floor next time.,and keep your hose in back of you or over your neck
and a drip rag for the cup, no matter how expensive the cup there is always a chance of a drip on that expensive new paint
if you can live with the paint ,and want to buff out the orange peel , maybe a couple more coats of clear to sand evenly would help