Now you be careful with your mega-nesting hun!

If the walls are ok a scrub with sugar soap (gloves on) will be fine.

You will need a brush to cut in - there are ones designed for it.

I hate rollers, they flick paint everywhere and it can be hard work maintaining the right pressure. When you go to Bunnings for your supplies check out the uummm whatsit called - umm pad painters I think they are called. It looks a bit like a mop head and its HEAPS better to apply paint with rather than a roller.