Simultaneously?
Twelve paint brushes, maybe? :
Two for blacking out 8's
Two for painting 7's
Two for blacking out 1's
Two for blacking out 0's
Two for painting 0's
Two for painting 9's ?
Or on the first night did they settle for 8 brushes and make do with the 09's offset a bit to the right, then let HD give them a final tug with his Reliant Robin?