I've never required a self-check.
The one time I've had lice was in the 8th grade. My mom had noticed that I'd come home from school with an excessively itchy head (specifically that I used the coarse bristles of a hairbrush to scratch at my head) and made the confirmation.
One treatment I recall we tried as it was suggested by my best friend's mom was to soak the hair in vinegar and wear a bag over one's head for I believe it was 30 minutes to an hour. We went with a shower cap rather than a bag.
The idea is the suffocate the fuckers with the bag or shower cap and the vinegar is to loosen the eggs or nits and possibly kill the nymphs, the young lice not yet mature enough to lay eggs.
https://headlicecenter.com/head-lice-vinegar/
In general, however, eliminating the nits is a separate treatment from getting rid of the lice.
I was not aware of scalp fungus or dandruff's relation to fungus until I read this thread and did a Google search but I can almost guarantee you that if you're finding dandruff shampoo effective and more obvious if you're not seeing little black dots rain from your head when you wash your hair, it's not lice.
Since Dandruff is most often caused by a fungus, if you're not noticing skin flakes than it sounds like some form of pre-dandruff infection if that exists.