i have a 40 year old house where i have spent a couple weeks bogging and sanding walls with jointing compound and even replaced a couple walls.
i have now filled all dents amd imperfections in the walls and sanded them all flat ready for painting. in some places i have just needed to sand the old paint a bit.
do i need a primer or just slap the new paint on now?

also when i use the roller to paint it, what is the best way to roll it on? all in one direction or do you have to go over it twice in the opposite direction before it dries?

also, how often to you have to clean out the roller??

there, 3 questions asked waiting for answers.

 

You use primer on any new drywall, and on any patches you have repaired on existing walls. If your old surface was painted with a high gloss oil paint that is very slick to the touch, those walls would likely need a primer as well to help with adhesion.

When you roll the walls, it's best to use a paint pole on your roller handle, and paint from top to bottom, then back up again, then back down, moving around the room whichever direction you prefer- I like clockwise. Think of it as painting a W on the wall. The only reason you would have to go back over the areas you just painted would be if you missed a spot, or if your roller is leaving a heavy paint line along the edges of the roller- something that often happens if you are pushing too hard, squeezing paint out of the roller cover... or using a cheap cover that fuzzes out on the ends. You can lightly backroll the wall to minimize these sort of lap marks. I pretty much backroll everything I paint because being colorblind, I'm always afraid I'm going to miss something if I don't. Hopefully you've got better eyes than I do!

I clean the roller out when I'm done painting. A plastic bag over the roller will keep it fresh overnight, provided you squeeze it onto the roller and try to twist it around the handle so that it seals the air out.

 

Absolutely you must prime the repairs. If there's as much as I am imagining here, I'd just go ahead and prime everything.

 

Yes, you must prime the repair areas
And it does sound like there's enough spots that the whole wall might be a good idea

Up and down, N, or W, pattern rolling doesn't matter too much
Whatever works for you
And you can go side to side with flats
But, eggshells and semi-gloss you must finish up and down, so it's not really a good habit to go side to side

There's usually no reason to clean out the roller until you're done painting
Unless there's a high risk of, or actual contamination, or other factors, it could be saved for the next days work if you'd like

 

I agree, I seldom wash up a roller until I'm finished, of course dried paint on the roller or accidently bumping the floor and getting dirt in the roller would necessitate cleaning.

Because it tends to be faster, I usually slop the paint on the wall and then gently roll over the wet paint when I've used up the paint [on the roller] to smooth it out. The main thing is to get complete coverage and keep a wet edge - flat paints are more forgiving.

 

ok cool, i need primer, wasnt sure. when you say keep a wet edge, what happens if i dont?? i have a small wall that has a door frame in it im not going to finish for 6 months, im wondering if i should paint that wall yet or not? im going to rework the door frame and the wall will need painting about 30cm from the frame edge again in 6 months, should i just paint it now and repaint the wall around the frame in 6 months or leave the wall and paint it all in one go later? im wondering if it will look funny having more layers of paint around the wall near the frame or not

 

I'd go ahead and paint it now, if the touch up doesn't blend later it is no biggie to repaint one wall.

 

cool thanks