You should continue to wash your hair according to any routine that works best for your scalp, and does not cause irritation or dryness. Over-washing the hair can be counterproductive, and should be avoided.
With Regaine®, you can apply this treatment either before or after you shower. If you are planning to apply the solution beforehand, it is recommended to wait at least 4 hours after applying before you shower, in order to allow the medication to fully absorb into the hair follicles.
However, you can also apply it after you shower, ensuring that your hair and scalp are both completely dry before application.