Advice on passing skin antiseptic studies for money?

The university I go to has a laboratory that pays really good money for participation in studies. The ones that pay best are skin antiseptic studies, which require you to have a certain level of skin bacteria to participate. I’m thinking about signing up for one that pays $550 if you are eligible. My problem is they I never am. I tried this study in the past and went three whole weeks without showering certain areas and still didn’t have the required bacteria to pass. Now I’m working a new job in customer service so there’s no way whatsoever I’ll do that. Surely there are some people here that are champions of medical experiments — is there any advice I can get to help me qualify? Thanks!