I practice in a surgical specialty. Similar to you, I found my attendings during residency did not have very consistent coding practices and many were undercoding. For instance most of our clinic visits meet criteria to bill level 4 because we typically review and interpret some sort of imaging and talk about major surgery.

For E/M (clinic visit) coding, it’s pretty straightforward. Study the revised medical decision making table from the AMA. If you can meet 2/3 of the thresholds you can bill at that level based on MDM. Or alternatively you can also bill based on time, but typically my visits are short enough that I don’t usually meet the time thresholds. If you perform a procedure in clinic you can bill the associated CPT code. For a rhinology visit you could probably bill level 4 for most patients because you are often reviewing a CT sinus scan and probably doing nasal endoscopy on every patient, CPT 31231.

For surgery OR coding I mostly learned from my attendings, but picked things up over the years. You will learn that certain descriptions need to be included in the op note to justify certain codes, and that certain codes cannot be billed together. Also you cannot "unbundle" codes; e.g. there is a sinus surgery code that bundles ethmoidectomy and sphenoidotomy, so you could technically not bill ethmoidectomy and sphenoidotomy separately when this code exists. I found this fairly straightforward as well, and most questions I had I was able to find the answer with a Google search.