So I made my first molds last night, using an r4 mx blank,
The top of the cap came out fine, but when I did my stem side of the mold, the stem didn't completely form to its full length.
It didn't reach the height it should have. I think I put way too much petroleum inside the stem, and that limited the silicone from fully filling it.
Do you have any advice for making perfect stem molds?
1) Stop using petroleum jelly - too easy to get overfill gaps and details, plus its inconsistent in application. Better off with a spray release.
2) If you're not pressure curing/casting then consider using a toothpick or something else small to apply small amounts of silicone to the inside of the stem on the master. Easy to trap bubbles in there causing exactly what you talked about.
3) If not degassing / pressure casting be patient and careful not to introduce bubbles into the sil as you are mixing. Pour in a very thin stream to burst existing bubbles as you fill the mold.
4) Happy to answer any more q's you may have but let's move it to the Making Stuff Together thread 
Good to know about the spray.
I would love to get a pressure pot, but I have to wait on that for a while.
Ill have to give it another go with the stem side tonight.
I did a very thin and high pour, and seemed to go fine without any bubbles in the molds.
Me limiting the fill of the stem from the overdose of petroleum was the only problem for now I think.
Im only doing the r4 mx and topre blanks first so that i'll have both negatives to place stemless sculpted caps on in the future.
Sorry about posting in the sale thread, and for this long quote-post.
Brought over convo from sale thread.
