Found this guy a few days ago on YouTube. He makes tons of Hammer tutorial videos on just about anything you could think of: a crash course on displacements, packing custom content (and making it) into your level, cubemaps, HDR lighting, optimizing, creating a 3D skybox, adding fog and much much more. He finished a 100 video series in one year last year going over countless topics, and started up another series again right after he finished that one. He's already into video 20 posted 5 days ago. The thing about his videos is that he explains what he's doing and clearly at that. He even offers 1 on 1 assistance free of charge (though donations are readily accepted). He doesn't do anything specific to TF2 - normally CS:GO or Portal 2 - but everything can of course be carried over. Here's his YouTube and website.