or a paint brush if you must. My choice for quick, large scale applications is a foam brush. Alisa Burke likes using a wall painting brush, particularly an old one if you have. They are really good for large surfaces. She uses latex wall paint too. I haven't done that much. One time when I was painting the floor in one of my studio spaces, I did this FREQUENT trick of putting out far too much paint. I'd mixed some acrylics with it to vary the colour. So "hey - why don't I just grab a foamy brush and put it on some watercolour book pages."

FABULOUS!
Most importantly ~ have fun.