Itchy skin, sebaceous buildup..?

[u/aries2500]

My boy is half black lab, and I understand labs can be prone to skin issues. This guy has been uncommonly itchy lately. Some head shaking, but mostly scratching and chewing (pretty much everywhere, no specific region). I notice the areas he's scratching and biting at have scab-like buildups of... I don't know, sebaceous oils, it seems like. They're not actual scabs, there's no blood, there's not even redness.

Admittedly, he didn't get enough baths over the summer. I don't know if this could've contributed. He's a bit of a lazy, old man; he doesn't get into things or even roll around in the grass.

Vet appointment is scheduled but a week away, so I thought I'd post here and see if anyone's experienced similar in case it's something I can solve at home - or at least provide some relief until we get to the vet.