Vince, you probably have read this but I will throw it out there for others to read also. https://www.excelmale.com/forum/showthread.php?2168-Raising-DHT-with-injections
Yes, putting a small amount of a "Cream Transdermal" on your scrotum can increase conversion, via the 5 alpha-reductase enzyme, to DHT.
Make sure it's a cream base and not gel as it can and will burn your skin and your scrotum is the last place you want that to happen.
Some clinics like Defy sell testosterone creams for just this type of application.