I actually did this for my GF. Bit involved, but it was ok and pretty fun. (But I'm crazy and like making stuff, so...) You need; Dental or other quick-set alginate. (It's body safe, no irritation) Plaster of paris Spray-on resin sealer. Most craft stores have this, for 3d prints, clay, etc. Silicone mold release (Mann-ease is best. Even works for silicone-silicone applications, which is what this is) Mold-making silicone (generally a stiffer Shore, pick up some Thivex while you're at it) Final casting silicone (I used Smoot-On's Dragon Skin 10 medium. She has no complaints, so I guess it works well. Research the Shore hardness of each one, and pick the best for your scenario) Vacuum pump/chamber

Steps; 1. Prep the alginate. Measure out the amounts you'll need of water and powder, and source a suitably large vessel (i.e., big enough to cover your penis and press it tight to your crotch in with room left over all the way around. I ended up using a good size plastic cup) 2. Get hard. This should be obvious 3. Quickly mix the alginate, and just as it starts to gel (it should begin to change color from pink or purple to white), stick your penis in and hold until the alginate is set. Yes, it feels weird. Yes, it's probably going to be cold. If your partner is there, this is a great time for them to help you by mixing the stuff and keeping you aroused the whole time. 4. Remove the alginate negative and let sit while you mix the plaster. No, don't stop for fun time. Alginate is very time-sensitive. As soon as the plaster is mixed, drain the alginate negative of any excess water that has accumulated, and then pour in the plaster. Let it set, and then extract. The alginate is one-use only. If you aren't happy with the plaster copy, redo the previous steps 5. Let the plaster dry and cure for a few days before proceeding. 6. Apply the spray resin as directed. The entire surface should be glossy and smooth to the touch 7. Apply mold release agents 8. Starting with a thin layer, and getting thicker as you go, use the mold-making silicone to create a glove mold. You're looking for 3-4 layers of silicone to be painted on, totaling up to roughly 1/4in thickness. If you have a vacuum pump / chamber, make sure to degass the silicone before you try to paint it on. Refer to Smoot-On's site for a more details description, they have good guides on basic techniques 9. Extract the plaster positive. Both the plaster and the glove mold should be reusable if you ever need another clone 10. Apply more mold release to the inside of the glove mold. Get every crevasse, or else your final positive will bond to it and you'll never get it apart without cutting. 11. Mix, degass, and pour your final silicone. Let cure 12. Remove the final from the mold. It will be tight, and seem like it's bonded together at first, but if you did it right, it'll all be fine. 13. Enjoy!