I can not speak directly to this issue and my apologies on the sarcasm.
What I can share is I have read that it can take three weeks of taking hormones to suppress natural production. There is a theory of cycling out there where the user uses short chain steroids and or orals for three weeks on then three weeks off. In that same post they also said a person could do two on four off. They very specifically said the user had to run pct on the off weeks.
Now my disclaimer, I am new to this end of the bb world. I can only regurgitate what I have read. I do not know anything from experience beyond my one cycle of actual juice. I have cycled prohormones before but that irrelevant in this case.
Try reading up on hcg it is supposed to help with limiting suppression. Weather that includes hpta or not I do not know.
All that said I know everyone on this site will tell you that you are too young to do juice.
As far as topical application goes if I were you I would read up on androgel I am fairly certain there would be something mixed in to make it topically absorbent. So applying anything that is not ment to be topical might just be a waste.