The core of the program is very simple, DHEA as micronised powder or cream, Progesterone as raw powder, gel from capsules or cream. This is the key to the whole thing. How and why are already explained quite well. DHEA and Prog couple well with also estradiol gel. This I would say is the simplest way to do the topical protocol.
What I do differently is adding absorbtion enchaners, main piece is DMSO cream which has low to moderate concentration, I've used 20% and 25% versions. Dermarolling also boosts absorbtion and it might have an effect on hepatocyte growth factor levels as well as it does micro level damage to the skin. Also I'm doing the caynne extract with Bovine Ovary and the 70% alcohol in it also helps to soften the skin barrier which allows greater absobrtion, as does estrogel as it also contains stuff to aid absorbtion.
This I think is very useful as there are multiple ways on how to do it, so even small doses can become rather effective.
I'm also using Red Clover extract the way Lotus has outlined, it works in multiple ways, it does cool stuff with prog, its a PPAR-y booster, as is Volufiline. (PPAR-gamma is part of the protein chain that deals with adipogenesis, that's fat cell formation.) Local IGF-1 (insulin like growth factor one) levels can be helped by using topical vitamin D3 oil. HGF levels are likely affected by dermarolling and capsiacin from cayenne extract, this hasn't been studied or I haven't found such study, but experiementation has been promising.
I just yesterday started to add ten drops of ginseng extract the the topical mix, knowing that it deals with breast growth hormonal pathways.
Anyway, this got a little drwan out as well, but that first paragraph is the shortest answer to your question. If you want to know how and why exactly, then you have to take your time and read. Its been all laid out here before and even more is on Lotus's Project X thread.