What is the cheapest way to brighten a basement workshop?
Painting the walls will help, but if your workshop is anything like mine, you're going to cover a large percentage of the wall area with workbenches, peg boards, machines, shelves, etc. And all the paint in the world won't help if you don't have adequate light sources in the first place. So spend money first on lighting, and then on paint if you have funds left over. Using higher quality lighting, and preferably several different types of lighting, will make working easier and more pleasant, so it'll be money well spent.