If you lack the skills for paid work, volunteering is often the easiest way to get the skills. After learning for a semester, you may be worth employing. Even if you volunteer, you are asking the faculty member to commit a fair amount of your time to your education, so you'll end up knocking on a lot of doors this way as well.

Nick's tip: the more senior the researcher, the less likely that they'll have time to help you learn. Start by asking junior faculty (assistant professors) or postdoctoral researchers.