I expect you need a steadier hand than I have to use a brush at the ceiling line. I used only a brush when I first started painting so I know it can be done. The tool just seems so much quicker for me. That is what most customers see first so it has to look good. I can usually tell the expertise of a painter just by looking at that line. Yes, Klean-strip does the job, even on paint that's been on a while.