Hopkins wrote:

Someone mentioned using a 3" or bigger brush. No -- a 2 1/2" angle sash
brush is the best all-around thing to use for interiors.

Agreed.

You going to have to experiment a bit with how to load the brush.
Obviously you want to scrape off the excess paint, but how hard to
scrape [i.e. how much paint to leave in the brush] is something to be
determined -- as you get used to cutting in you may want to carry more
paint per brushload.

Scraping off the paint is the worst thing you can do for the brush.
Paint should be poured from the can into a smaller container than can
be easily held. The brush is dipped into the paint about halfway up
the bristles, then it is lightly slapped against the side of the
container to knock off the excess paint. You want the brush fully
loaded, scraping the brush takes off too much paint and damages the
bristles of the brush. If you've ever seen someone's brush that has
all of those short hairs sticking out from the sides, they're scrapers
and not slappers.

R