This first picture shows the two pieces we are joining together. You first want to test fit the pieces together to make sure they fit right. You then want to pull the pieces apart, leaving a gap like so.

For the next step, I applied Plastruct Plastic Weld to bond the pieces together. I simply apply a little bit of the Plastic Weld to the two pieces by swiping the brush down the seam line on the edges. The Plastic Weld will melt the plastic edges of the two pieces to form one seamless piece. When you push the two pieces together, you will get some excess glue/melted plastic to seep out of the seam line. This is normal and is actually what you want to happen. Once the Plastic Weld has dried, you then can sand the seam line smooth.

50% of the time, this is all that I have to do to get rid of the seam lines. Unfortunately, this was not one of those times.

Since the Plastic Weld trick did not work completely, I had to apply putty to the seam line as seen in this picture. I don't thin my putty as some do. I just apply a good amount all over the seam line. Once applied and the putty is dry, I then sand once again.

Here you see the head sanded and primed. As you can see, there is no more seam line.

I picked this technique up from Duncan, aka Gouf, the owner of the website Kitbash. I have a link to his site on my Links Page if you are interested in checking out his site.