I don't want to take anything away from proper bricklayers, who I know would do the job ten times faster and without any concerns about the quality of the end result, but if I wanted to build a small garden wall, or (as in this instance) I want to build a simple two-course plinth on an existing concrete base for a simple timber building to be built off, how feasible is it to get it "good enough" if I buy a few basic tools (line, trowels, etc) and take my time with it, making sure it's all level/plumb?