Transfem

Testosterone cream can raise your blood levels of T, and cis men who use testosterone cream find that applying to the scrotum and genitals has better absorption and higher blood levels than applying it elsewhere (like arms or thighs).

I haven't personally used T cream, but I suspect it's a matter of dose and frequency - if you use a small amount locally on the relevant tissue and not too frequently, hopefully it won't be a problem for your blood T levels and the phallus tissue will still benefit.

The problems with Dr. Powers aside, this might be helpful:

https://old.reddit.com//r/DrWillPowers/wiki/compounded-medicines#wiki_genital_atrophy_reversal_cream

This cream is applied topically to the penis/scrotum once a week at bedtime in AMAB people experiencing erectile dysfunction, painful erections, tissue atrophy (shrinkage and thinning of the skin). It is used with escalating frequency approaching SRS for optimal tissue health. Post SRS it can be used weekly during a dilation session (by coating the dilator) and sometimes can help achieve additional depth due to increasing tissue elasticity.

Manufacture

Testosterone #31 Formula - 2.5 mg/g (0.25%) - Cream (Versabase)

Packaged in a clicker style pump dispensing 1 gram per pump.

(Empower will not make 0.25% concentration, so they make 0.5% and the patient only uses one half gram) - Feb 2022

changed strength from 0.5% to 0.25%, Oct 2021

Usage Instructions

SIG: Apply 1 gram to genitals once a week at bedtime.

tl;dr get a prescription for 0.25% testosterone cream, apply 1 pump once a week to the genitals before bed

Might also check out:

https://old.reddit.com/r/Trans_Resources/wiki/hormones/transfeminine/index#wiki_erection_abilities_and_shrinkage

A number of people try to fine tune HRT. Keeping levels of t in the upper part of the female range, around 40-50 ng/dl, may help with erection abilities, and also with libido and o abilities. With lower levels those may be reduced, which some people prefer. Levels well below 10-15 ng/dl may not be advisable though because there may be issues with level of activity, tiredness etc. Explanation here at 00:48:45 .

Discussing Bicalutamide as anti androgen may be an option, it blocks t and DHT receptors but not production so a few things may remain more functional. Here was an article that could be discussed.

And some people add bioidentical progesterone after one to two years, and after breasts are in Tanner stage 3-4. It may also help with libido and o abilities, here and here was more.

Otherwise a number of people ask for Viagra or Cialis. And many people, cis, trans and pairs, use a Hitachi magic wand. It is designed to stimulate a whole area and may make for less dysphoria.

And the skin may become thinner and more sensitive. Sperm production may be strongly reduced on a HRT with levels of t in the female range, and parts may go into an in between stage. There may be more moistness and also changes to smell etc. Here was more.

There still may be a few sperm around on HRT though so using protection in case may be advisable.

Having erections from time to time may help to prevent some shrinkage. Additionally there is a cream that can be applied locally. And some surgeons from the time of a standard PI recommend to stretch it regularly in a towel. And anecdotally on a HRT without anti androgens there may be less shrinkage.

Note: testosterone is a controlled substance and is harder to find DIY, so this generally requires getting a Rx from a doctor (hopefully you have a supportive endocrinologist overseeing your transition that can help here).