How should I determine MACO formula for Topical Solution?

Dear, All

I doubt about determine MACO formula for topical solution. I already read " Setting Cleaning Validation Acceptance Limits for Topical Formulations" Article of M. Ovais. I thought it can’t apply with topical solution because solution can’t comply with FTU. It also can’t use MACO formula of tablet due to lack of therapeutic daily dose. How should I do?

Thank you,