Hi Aaron. Trust me, you are not alone on the scalp acne. I am a 29 year old male, and I have been dealing with it for years.
I used to use some hair products in my hair, and stopped that over a year ago to see if it helped. Nope, still break out, 90% of the time on the back area of my scalp, sometimes on the sides/top of my head.
I use Head&Shoulders shampoo, let it sit on my hair for a few minutes in the shower. My hair is very short (I shave my whole head down to about 1/2" length).
Scalp acne is a result of too much oil, just like it is for any other acne. Your scalp develops oil just like your face, neck, back, etc. It could be a case of folliculitis.
I have mentioned the acne to my regular doctor AND a dermatologist, and they basically blew it off as no big deal. It is a big deal though, since the lesions can be very deep and painful.
Sorry I don't have any positive advice, but nothing I have tried has "cured" my scalp acne.
PS I see other guys that also have scalp acne...it's easy to spot on guys with short hair.