There are many tutorials that capture everything you need to get flawless bakes. Understand how a lowpoly works, what transers well into a normal map and check the few clicks you need to know in, for example, xNormal.
Really amazing.. I've been trying to recreate this using your method, but I'm finding it practically impossible to come up with the shapes needed to boolean subtract.. For example, the part where the shell is ejected.. Spent about 6 hours trying to boolean that and I just can't figure it out. Any tips?