I like to make the electronics for my models completely from scratch, mostly because I like electronics but also because I can add as many features as I like provided I can fit it into the model. This works for me but it doesn’t suit everybody and a popular alternative to to buy Siku Control 32 models and gut them for their electronics. 97JackBlack on YouTube is an example of this method perfected, he has a huge collection of static models converted into Siku Control 32 models. Here are some examples of his conversion work.