Cutting in a three dimensional corner?

[Meeeeeeefsk]

Hi all, has anyone got a good tip for cutting in the corner where two walls and ceiling meet?
I can cut in anywhere else just fine, but no matter how I orient my brush I can never seem to get it to make a perfect 90 degree corner; the edge is always rounded. I bought a Hamilton Expression Precision brush that has a triangular cross section, and is angled, it's better for the job but still not perfect.

[Grendel]

I don't claim to be a professional decorator , more a joiner that does a few decorating jobs.
Right or wrong this is what I do. Ceiling painted first with the paint lapping onto the walls . I normally keep the top edge of the wall paint a couple of mm down from the ceiling . I find it easier to use a thin brush with long bristles and bend it into the corner and sort of give it a !ittle side to side wiggle which I find spreads to bristles out to a finer point for getting closer in.
Probably one of the pros will be along later when they stop laughing...

[dynamod]

An angle sash brush with decently long filaments is important, but perhaps more important is that the paint is at the correct viscosity. If you're struggling at all, thin the paint slightly to get it to flow out a bit more. Full strength emulsion can be quite tricky to get into tight corners and cut straight lines with.

[dewaltdisney]

I am useless at cutting in and Frog Tape may help. It is a low-adhesion tape and firms up when painted into a hard edge. See https://www.frogtape.co.uk/why-choose-frogtape/

DWD

[Grendel]

I don't suppose it matters that you can't cut in as don't you just paint everything white ?

[dewaltdisney]

quite right. Although I did a single feature colour wall at my son's house in the past.

DWD

[Bob225]

Tape it and paint it, frog tape give next to no bleed, 6" scraper also does the job as well