Yes!
I have few on the shelf, waiting. I did make two actually; one went bad during the mold process. Seriously, rub one off, wait a while and then do the mold.
Other one came out half-decent.
Good thing the sets mentioned on that site seem to have two mold bags with them! Taking the mold is the trickiest part; if you have a partner, great! If not, really read the instructions, have everything ready. Have something very erotic to keep you in good erection.
That's all I guess. As there are two molding bags, you can fail once, but if you get it right once, you can probably do it right twice; second time you could make a cast with chocolate perhaps. (Those kind of sets have been and still are for sale I think. A tasty treat to give, hehe.)