Hand-made is nothing more than a kind of clay sculpture, using different materials, turning it into AB soil and so on, and then copying resin. Both production and painting need a certain artistic foundation. You can consider the sculpture major of the Academy of Fine Arts, and of course you need a certain art foundation.

As for Gundam, it is a toy in general and belongs to mechanical design. Some universities have industrial design major in toy design, you can learn about it.