I am obviously neither the first nor best person to make DIY Funko Pops. A pretty good introduction to how to do it can be found here: http://thefunkustomizer.blogspot.com/p/blog-page_17.html.
1) When choosing the Pop, which can all be found here https://funko.com/products/all/brands/pop, keep in mind that the head and the body can come from different Pops. This opens up all kinds of options for making your Pop.
2) When trying to pick the right Pop, picture in your head the episode or outfit that you want your pop to invoke - it makes it simpler to wade through the hundreds of Pops.
3) Depending on their release and popularity, Pops come in a range of prices. In general, all of the Pops in this blog cost less than $11 each.
1) Wash in warm soapy water, rinse, and dry.
2) If you need to remove the head, boil water in a container that can fit your Pop. After it reaches a rolling boil, take it away from the heat source and throw your Pop in. Let it sit for 2-3 minutes. This will soften the plastic making it much easier to pull the head off.
3) To pull the head off, just grip the circle on the bottom and pull. If it doesn’t come off easily, stick it back in the water for a few moments. This is what it should look like. If you end up removing the ring part at the bottom of the head, don’t worry - you can always superglue it back on.
1) Have a wide variety of brushes.
2) Use painters tape to block the sections you don’t want to paint.
3) Use acrylic paints. I found these at Michael’s for less than $2 a bottle.
4) Paint everything white as a sort of primer.
5) In general, it will take about 2-3 coats to get the coverage you want.
6) Seal the paint using a clear, matte spray paint. This will prevent the paint from getting scratched or peeled off of your Pop.
I didn’t want to get into sculpting, sanding, and reshaping the Pop. I was fortunate that I found base Pops that were very close to what I wanted for my final pop. There are other places on the web that can talk more about those advanced maneuvers. The most advanced thing I did was make glasses for Giles using 12-gauge aluminum wire and painting it gold using a Sharpie paint marker.