What is the best way to achieve clean line when painting?

Your best bet is to tape, unless you're really good at free handing it. Walls are not in a perfectly straight line. At least mine aren't.

https://www.thespruce.com/best-and-worst-paint-edgers-1822406

Try painters' tape! I have problems with straight lines, myself. You can also hold a piece of wood or cardboard as a guide to paint right up to where the walls meet. A third option would be to pre-paint molding to use use along the ceiling/wall joints and let that cover up any slips. Good luck!

I run a straight line of tape on the walls just below the ceiling (like 1/4") and paint the ceiling color into that space. Your eye doesn't see that the paint extends onto the wall, it just sees a straight line. This is the best way I've found to fix that wonky line issue.

When I painted my walls (popcorn ceiling above) I used a throwaway pad painter from HD with the Styrofoam back. Worked like a charm when I eased up to the line the ceiling made. You just have to be patient but it took a lot less time then taping off. They also make a pad that will fit on an extension pole that has rollers built in to keep it off the ceiling or trim whichever you are painting

Hello Jz, Have you tried using painters tape, or better yet some 'Snot Tape (which is a new product on the market) or Frog Tape? You can put it on the top of the darker wall, paint the edges of the ceiling, then go back while the paint is still wet and pull the painters tape off, et voila, a clean straight line :) (Although most of the videos I have seen ... and what I used to watch my mom do when I was a kid... was paint the ceiling first then paint the wall

Thanks ofr using Hometalk for answers, and good luck with your project! :)

https://www.youtube.com/watch?v=-sivZ6GNjBg

https://www.youtube.com/watch?v=dBRGftw_xRA

Search on youtube, there are some great painting tips on there

I have used the same thing that R Walter suggested, it does work really well. I did the ceiling first, then tackled the wall with that tool. Made the painting real easy.

Did you try painter's blue tape

Take you time on this; trim painting takes as long or longer than painting the walls. You may not be using a trim brush. A trim brush is slanted. Load your brush with paint and the paint just up to the ceiling; but not all the way - about a half inch to an inch. Then immediatly in that area: Put some paint on your brush and then wipe one side of it off on the inside of the paint can. When you go to trim now; there is less drag from the area without paint and the brush will move more smooth. I also, just dab a bit of the paint from the brush on the wall below it; to make sure I don't have too much on the brush; and them use the little bit extra that I dabbed to trim. Then blend in that little area and move to the next area.

use GREEN painter's tape it is flexible and sticks to uneven places. Lynne

Also, I have an aluminum strip I use some times. Wipe after every paint brush.

Also, buy an angled paint brush and carefully push until it is even with the wall you are painting. Lynne

Painter's tape.