When I was painting the pump house earlier this week I wanted to re-use the same paint tray for the floor paint that I had used for the wall paint.
Here's my solution. I simply slid the paint tray into a kitchen garbage bag. Then I poured the floor paint into the covered tray. Clean up is a snap because I just turn the bag inside out after I have emptied the extra paint back into the can. I have used grocery bags to do this but you have to be very careful about any printing on the bag. The ink can actually bleed into the paint, turning it into a different color! Believe me, it's not a pretty sight.