Any regular Dean probably has the most training, since they had access to books and journals and the internet and class. Smol Deans, on the other hand, are forced to be innovative, and come up with unique solutions without any resources to lean on.
BL Dean has taken to his mechanical background rapidly, but he has a lot of catching up to do, relatively. Trails West has been inhabited for years, so a lot of the projects he could possibly work on have already been done. He would have spent a lot of his time making sure repairs were kept up, while he wasn’t out getting supplies. He and Jacob would be a bit behind the full-sized Deans.
The Dean in BC has spent the most time working on the walls at Baker Street, since the people that lived there before them left quickly, and hadn’t put any work into the place. He’s also got Sherlock as an assistant, who might be a bit offended to just be Dean’s ‘assistant,’ but is certainly knowledgeable on his own on a variety of subjects. He’d give BA Dean a run for his money!