Take a clean plastic handle paint roller and slide it on the handle of the roller. Sometimes it is hard to push it all the way onto the holder so tapping the end will move it all the way onto the roller handle. The polyacrylic paint roller will not load evenly if the brush is not all the way onto the handle. After the ceiling is rolled, do the cutting in for the walls and do one wall at a time. This way if you are working alone you can do the rolling of the wall while the rows that you cut in with the paint are still wet.
Dip your polyester paint roller into the puddle of paint in the paint tray and the roll off the excess on the slanted part of the roller tray. Start the walls in one corner and with the roller paint the letter W. Work the paint from the W to the top of the wall and then work the paint at the bottom of the W to the bottom of the wall. If you would rather paint vertical lines from top to bottom be sure to overlap the rows of paint to blend the paint as you go along. If the rolled paint becomes spotty looking or is difficult to handle it means you need to get more paint on the roller.