How difficult are age waivers to get for Army OCS for prior service/active enlisted?

Age waivers are required for any OCS applicant over 28. Talk with your recruiter. If your pt scores are good enough you won't have any trouble. My recruiter had processed waivers up to 36 and "heard" of waivers at 37.
I was accepted by the OCS board and I just turned 34.
Don't let age stop you if that's what you want to do.

You don't need a waiver if you commission before age 34. At your present age, you can enlist in an MOS of your choosing, serve a couple of years, then apply for OCS when you turn 32 or even 33 as long as you can get through OCS before your birthday. I enlisted at 27, served about 2 1/2 years in the Rifle Squad, then applied to OCS. Actually, at the time, the Army was expanding the Light Divisions, my Brigade would solicit all qualified enlisted to attend OCS. The second time they asked, I said yes.
A couple of years in the ranks should give you a good idea if you like the lifestyle.
You still need to make all the qualifications. A 4 year degree, over 110 GT score on the ASVAB, capable of getting a Secret Clearance, and as Enlisted, a passing score on the PT test and passing the height/weight requirements.

Unless things have changed and Im not finding they have in the regulations For regular Army, You must enter active duty training prior to their 30th birthday (that means to receive your commission as an officer and move on to your net training unit assignment).

Army Reserve officer
candidates must enter active duty or ship to training before their 35th birthday

Age waivers are granted on meritorious cases only, and for that, you best be a shining star in all measurable categories and be in need by the service.