Paint straight line at ceiling like pro without tape. Paint ceiling first, wrapping corner. Take ubiquitous back edge and gently score mark. Just use corner as naturally flowing guide. Using brush loaded with paint, just cover line.
How to Caulk Moldings! caulk moldings DIY - the tip about painting over the caulk is right on. Our non-painted caulk in our bathrooms attracts dirt & hair. Will have to fix that when we repaint our bathrooms soon.