I have tons of experience with this, since I had a diagnosis of severe disfiguring acne as young as age 9. It was hereditary for me, my Dad had the same thing, and one of my brothers as well. I will be prepared to take care of it should my daughters have it!
The first thing is to please, (I beg you) realize that this is a chemical/hormonal problem, and has NOTHING to do with hygiene or diet. Sure, hygiene can contribute to acne, but persistent hereditary acne, especially pubescent acne, has NOTHING to do with hygeiene. In fact, regular washing can irritate acne and make it worse.
There are basically two kinds of OTC meds for acne. Salicyllic acid and benzoyl peroxide. Lots of people are allergic to the peroxide (including myself) so be careful to use it on large areas, because an allergic reaction is VERY painful. I know this from experience. Benzoyl peroxide should only be used for spot treatments and difficult blemishes. Believe it or not, you want a moisturizing wash because when the skin gets over-dry, it makes the acne worse. I have oily skin too, but I need a moisturizing wash. However, washes only go so far to treat acne, as acne comes from within. Washing gets rid of the dirt/oil, but not root of the problem.
My first line of defense when/if my daughters ever start to exhibit acne will be the dermatologist. I have permanent scars everywhere from my acne- dermatologists know how to minimize that, and keep it from coming back. They will tailor a treatment plan to your son. I of course had extreme treatments for extreme acne, but there are tons of milder prescription ointments, gels, and washes on the market for teens and pre-teens like your son.
Again, please be patient and understanding and good luck!