So here's the process I used to mold and cast the Nosferatu Jr.
My buddy Jerome Ranft showed me this molding trick and it works really well for smaller pieces.
There is a few other molding techniques I use but this one is pretty slick...
So here it is in a nutshell...

1. First I figured out how the piece could be cut in half...Some more complex pieces may not lend themselves to this without cutting off parts and molding them separately. I built up clay around the piece where I felt the separation line should be...Often I'll use a sharpie to make a line where I want to build the clay up to...
2. I use Lego's to build walls around the whole piece. Then make sure the clay is up to all the walls so the liquid mold rubber can't run down between the legos and the clay. I couldn't find Lego brand blocks so there was a tiny bit of space between the blocks...Because of this I smeared a thin layer of clay in to all the cracks...
You'll also notice I made indentions (keys) in the clay,so that the mold halves fit together, or register.
I also made some vent tubes out of clay from the knee cap to the hands and also on the bottoms of the feet. This will make the resin flow easier, eliminating air pockets...In addition to this I made a thick tube coming from the butt which will be the main pour area.
3.Just another shot from the side to show the build up with the blocks...
4.A two part silicone rubber molding material made by Polytek. For this I used Platsil 71-20
This is one of the easier mold rubbers to use since you don't need to use a gram scale. It's a simple half and half mixture...
5.I use 3 separate cups to mix the thick liquids. I pour one of each in separate cups and then pour the thinner liquid in to the thicker liquid's cup. I stir with either a kitchen spatula or a tongue depressor depending on the amount of mold material to mix. I mix very thoroughly and then pour this in the third cup. This ensures that all of it is mixed and you don't miss any on the bottom or sides. I thoroughly mix this some more and pour over the piece...
6. I make sure that I use an airbrush to blow the liquid in to the tight areas and ensure that there are no air bubbles on the piece...This will save a lot of headaches down the line.
7.The first half is done. I make sure that the blocks are stacked high enough to give the piece at least 3/8 inch of rubber or more covering the highest peak of the piece.
8-9 Flip the piece over and take the clay off the piece. You'll probably have to take some Lego's off to get at all the clay.
Then I take a cheap paint brush and smear a very thin layer of Vaseline all over the cured rubber and the piece so that the new rubber won't stick to it.
10.Lego's are stacked back up again...I pour up to the top just like the first half. Again, I make sure I have at least 3/8 inch of thickness of rubber covering the piece at it's highest point. If you look closely you can still see the clay for the vent tube from the knee to the hand is still in the rubber. I push it back down in the tube so that it stays hollow when the other half is poured. (does that make sense?)
11.Both halves of the mold pulled apart.
12.Another Polytek product...This is a two part resin that I use to cast my pieces in. I use Easy Flo 60 or Easy Flo 95...
The 95 is a slower setting resin while the 60 sets up quickly...
13. Before I pour the resin in, I tape up both halves with clear packing tape. Big rubber bands are good for holding the halves together as well.
14.Once the resin cures, the halves are pulled apart...
15. The cured piece ready to be dremmeled etc. Often there will be seam lines to be taken away along with the vent tubes and pour tube...To patch any air bubble holes, I use Apoxy Sculpt.
Hope this gives you a fun way to mold your own work!
If you have any questions about any of this, or if what I wrote is confusing, always feel free to message me...