I initially used progesterone in coconut oil applied to the scrotum, ~7 mg. This gave good results but seemed a little messy and imprecise. The product is easily obtained on Amazon.
I switched to an injectable form obtained from AllDayChemist. I use only 0.6 mg per day. It sounds like
Defy is willing to prescribe it, so that will probably be the source of my next batch.
I rejected oral dosing for the reason stated by
@JA Battle.
I think there's something to this, and the list of upstream hormones that may be disrupted by TRT is getting pretty long: LH, FSH, GnRH, kisspeptin, progesterone, pregnenolone...