First of all if u want to make hybrids you need to have virgin females, so you will be sure if the female mated or not. Its 5 months that I am trying this thing, I took some in the wild at a lake near my home,….
(I’m not sure if they are Gambusia Affins or Gambusia Holbrook but as long as they look the same for me its ok, they are both Gambusia

).
,.... I captured only 2 big females ready to spawn, I raised the babies and now I have 3 virgin females and (separated) 2 males they are virgin too, hehe
In the same time I bread my guppies from the pet store, some standard red guppies, and I had from them a lot of babies but I separated two females hopefully still virgins.
Experiment A – female Gambusia with male guppy
Only one of the females survived and I put her together with the male guppies since they both were at maximum one inch long. Hoping so that they could get familiar with each other. But as long as the guppy started to have colors over his body. The female was always attacking his tail as she was hungry. I eliminated most of her attacks through over feeding the female, but even in this way the male was to scare do try and mate the Gambusia female. So she developed a lot of eggs and her belly was very large even if she was virgin, the eggs were transparent yellow and she didn’t get any black spots on her belly, but instead the spot were transparent and you could see through them the yellow eggs. After a month she spawns only unfertilized eggs. Which the male ate all of them hihihi time for revenge
So it was not a success or I need to find another technique for this one.
Experiment B – male Gambusia with female Guppy.
The beginning is the same as before trying to get virgin guppy females, I hope I separated them soon enough from there brothers, and put them with gambusia. Gambusia males were very active in mating and attacking female colored guppy tails, even here I tried to over feed them and the attacks were reduced. Now I have about 20 babies at 1 cm, I can’t tell if they are hybrids until they reach maturity, meanwhile I will try to bread them again.
If anyone is interested for photos let me now so I’ll try to take some.
Hope I was helpful to somebody