I have done this process many times with another brand doll I wont mention.
It was very easy and they also sent a two part mix you mix up and then inject into the breast .
It is actually quite simple ...
Now I would strongly like to mention to those that might not know..
This process is different depending on TPE or Silicone ..
If you are unsure then injecting just plain air is your best bet..
NEVER inject Silicone based Gel into TPE dolls ...You could end up with a terrible
pile of goooo for boobs as TPE and Silicone often do not get along well and cause the
TPE to melt down into a sticky mess.
I would contact the company you got your doll from and see if they have a special gel they use in there
TPE dolls ...
Also please what ever you do lol.. STOP injecting random household things into your dolls..
Again if you inject some random liquid soap or what ever people tell you to use into
your dolls and something should react with the TPE you could ruin your doll ...Seriously DO NOT DO THIS lol..
The company can guide you in the proper direction on how to fix this issue