Here’s a painting hack I learned from @HomeRenoVisionDIY (which is a great channel for DIY info).
When cutting in walls, don’t dip the brush into the can of paint as it will only cover the sides of the brush with paint.
Instead, fill a cup with enough paint to cover the bottom of the brush bristles. This will fill the bottom of the brush with paint and put a lot more paint on the wall, saving you time.