Hi Charlotte,
I have not done hair replacement myself, but I do know another trans woman who has. I have also done a little research for myself as well.
In my opinion:
You asked about waiting till after you start hormones. That might be fine, but you need to be doing things now. I would get on Finasteride and Monoxidil, like yesterday! I would also invest in a laser comb. The hair replacement people I spoke with during my research recommend this approach. Hair retention is better than hair replacement.
My next question is are you planning any facial surgery? Facial surgery will have an impact! If you are thinking of doing anything that would involve your forehead, it needs to be done first.
Hair replacement takes a while to "take hold." Depending how bad your hair loss is, it can take a couple of years for things to look their best. There is a limit to how many follicles can be done each session.
"Wispy" is a pretty subjective term. There is a scale for hair loss, it is the Norwood Scale.
I am not sure why you are not on hrt. Propecia is used by lots of men and any PCP can prescribe it.
Good Luck,
Elaina