Painting tips for staircase?

Submitted to General Questions

I've already gone through one gallon of Rust-Oleum Sure Color "Picket Fence" while painting my upstairs hallway and staircase. This is more work than painting a room! I'm covering a wedgewood blue color so it's needing another coat. What I'd like some advice on is, "How do I reach the high parts of the wall?" I've managed to use a roller extension but edging the top of the wall isn't going to work. P.S. I'd like to stay safe and secure!