Step 1

Take your normal tyranid head and cut off all of the head plates that you can. Then go over it with a file and smooth it out. It doesn't have to be perfect. Be careful when you do the area near the eyes.Really the only detail you're trying to keep is the whole mouth area.

Step 2

Just take a big wad of Green Stuff and create the shape of the back of the head. This also doesn't have to be perfect. Just get the basic shape, because you'll be going back over this area with new green stuff later to do detail. if you want to. If not, just make it as smooth as possible.

Wait until this piece is completely hardened before you move on to the next step (I wait a whole day), because you will need to hold the head from this part of it and if it's not dry, you'll have fingerprints all over it or you'll squish it into a different shape by accident.

Step 3

After the back part is hardened, take a new wad of green stuff, just a small bit and form it into sort of a triangle shape. Place it over the eyes with 1 corner over the "nose" and the other 2 wrapping around to the side.

The green stuff I used in the pic is the same as before, it's just a lighter green because I used more "yellow stuff" in the mix, just so I could show the steps easier.

Step 4

Now we get to the fun part. Take your sculpting tool (I just use the one GW sells) and squish the new wad of green stuff down all over the forehead part, and smooth it out and blend it into the back of the head. Keep going over it with your tool to get it nice and smooth. Don't touch this area with your fingers, or you'll have prints everywhere and you'll just have to go back over it again. You want it to look as smooth and rounded as possible.

Step 5

Last is the detail! You can skip this step if you're not sure you can do detailed work enough, but really I don't have that much skill IMO and I can do it fine, so give it a try if you wanna. For my heads, I squish a little ridge over the nose area and go back to the side of the head then have it turn up a bit.

You can make yours as detailed or not detailed as you want. If you want to try and sculpt it to look just like the ones in the films, go for it. But, what I'm after in mine is just something that resembles them and between this easy sculpt job and a mostly all black paint job, it's good enough for me :)