I think dutasteride plus RU would be a lot stronger than castration. RU did regrow more hair than proscar on monkeys. I think they applied it 5x per week. Who knows what vehicle is best, but alcohol PG is a very common vehicle. My brother uses alcohol oleic acid, since he can't handle PG.
Do you think you can spread 0.5mL over your whole head? If so, then it is $40 per month for you. I'd need at least 2mL for my whole top of head, and that is really pushing it. 3mL would be better for me. So it would be $240 per month for me. It is a lot cheaper if you buy the powder from Faith Eagle and mix it up yourself.
And this is still experimental. No 5 year studies. Just I think a 6 month study on monkeys. No reason you can't apply rogain right after applying the RU, before going to bed, unless you are sleeping with a woman.