In the past I always did the "while I'm doing this, how about doing that" approach that only leads to a permanently unfinished project. In software we call it "scope creep", where a project's goals change gradually and it is never done.
Daily driving my car has benefitted me hugely by forcing me to complete projects one at a time and then buttoning it up. Always a clean slate and a fresh start without worrying about this or that other variable. It's so much better and (counterintuitively) less work.
I would not even think about paint now, because you're not doing paint. You're doing the immediate engine tasks, will kick butt on them, and then when you want to think paint, think paint and take out the engine again.