I thought pyr0ball's mold design was simple and worked great as far as overall fit/finish and ease of use. However the socks it produced were about 1mm too long with the nozzle tightened down against the heat block. So I remixed it to have a shorter nozzle cover. This thing requires also printing the handle and cap from the original design here:
Using the resulting red high temperature rtv silicone socks is a joy. They fit very perfectly on the clone e3d heads, and they resist high temperature much better than the original blue socks I was tying to my clone head with wire. For example printing nylon at 260C, the blue ones got hard and developed a whitish discoloration. These red ones appear to not be at all affected even with testing long periods at 285C. The socks are also much more affordable; a small $9 tube of rtv produced 15 usable socks. My first sock lasted 97hrs of printing abs and nylon, and it was replaced because it was damaged from snagging on a curled up overhang. That sock looked otherwise new when I removed it.
Some molding tips:
The usual red high temp rtv you get in a tube at the autostore is all I'm using. To cure the parts fast I put the clamped mold inside an open plastic bag with a wet paper towel inside Don't wrap the mold, just let the damp towel give off evaporated moisture. It's also important to leave the bag open to let out the acetic acid that forms from the silicone curing. The resulting high humidity environment accelerates curing enough to pop the molds safely within 16hrs at room temp regardless how cold or dry your climate may be. You don't want acid covering your hotend. So before using the socks, let them sit in the bag to finish curing for at least another day or 2 after popping them from the mold (until they stop smelling like vinegar). On a side note, putting the bag in the afternoon summer sun I've pulled parts successfully after just 12hr, but the abs mold ended up warping so I stopped doing that. :D
I am experimenting with the use of "ironing" for a smoother surface finish on the part. The remixed sock was my first attempt. As you can see in the pictures the mold turned out nice, but not as perfect as I want. With 30% infill and 8 top/bottom layers at 0.1mm the ironing warped the abs a bit much where I can see faint infill patterns on the part. It was printed in a 50C chamber which would help this artifact along, but I still recommend trying ironing with more top/bottom layers and higher infill percentages.
As with the original thing this is based on, build plate supports are required on the inside part. The handle, top, and bottom external parts need no supports.