⟩ Tell us how you would paint if you are using a brush and not roller for painting?
If you are using a brush instead of roller then
☛ Use a primer for the first coat
☛ Take a half fill color bucket, dip 50mm brush up to one-third of the bristle length
☛ Then hold the brush at 90 degrees to the ceiling and paint a straight line, cutting between the walls and the ceiling
☛ Turn the brush parallel to the ceiling and drag the brush parallel to the ceiling without touching the ceiling edge
☛ Same procedure can be repeated along the bottom
☛ To paint the large and middle part of the wall you can use a broad brush.