Painters straight edge

Never use them, prefer a quailty brush (Purdy in my case) a steady hand, & same technique as below, hasn't failed me in just over a quarter of a century.



P:S: I'm not a painter, so our painter Astramax will be along with his tips.

 

I'm by no means an expert and not a painter by trade either but I tried one once and it created more mess (when you lift the edge up you can smear paint and it's also likely it will seep under the edge - your edge will probably be straighter than your wall/ceiling) so I decked that off, got a decent brush (Wooster silver tip 2.5 inch) learned how to load the brush and lay it off on the wall properly and never looked back (it did take a good few walls of redecoration though ).
One other thing, and sorry if I'm telling you how to suck eggs here but sanding the ceiling line helps massively also, as it gives the brush something to glide along. With bumps and divots it stops the brush flowing freely and that's where I found it impossible to keep a steady hand.

Good video post above, I spent ages watching that guy's videos over and over when starting out!

 

Thread should read 'Painters Steady Hand' .....comes with a lot of practise...Just hang on in there and of course a decent brush.

 

And a quailty brush.

 

Most people hate cutting in, but for me its the only part of decorating that I enjoy doing.
As previously mentioned, use a quality brush with a decent calibre, a 2.5 is ideal.