Welcome to the forum!

 Since you want to keep the stubble/shadow look all the time (that may change  ) you probably should skip the barber part and invest in a set of clippers. Wahl Balding clippers get pretty good reviews on here.

 Good luck!

Yep! just go with the clippers. Most clippers come with a set of guards for different length. Just start with something you think is long enough and if it is longer than you wanted, get out the next step down and repeat until desired length or if you want it to the skin but want to feel that rough hair don't use guard at all. Just take your time don't try to take it off like they show the military barbers on T.V.

By the way, a set of clippers if about the $ as 1 trip to a barber shop and 2 trips if you go for a good set.

Have a cheap set of Conair clippers that I bought back when I was just buzzin it down with no guard.  Has a beard trimmer attachment too.  Still kickin after all these years. 

Lichen planopilaris--
It is a problem you need to deal with a dermatologist about, there are treatments.  Talk to him/her to see if shaving you head might actually help the condition--as it does for psoriasis and similar skin problems.  My bet is that the dr. will say that shaving won't hurt.  You may want to consider an electric razor, at least at first until the patches are under control, a Cleanhead I think it is called is specially made for this. 
The hair on the back of the head is the most persistent even with the most developed mpb. 
Good luck, but I think Sly is your answer together with the ointments, etc. to control the inflamation. 

She did say having it in a pony tail didn't help but it makes no difference anyway since now when I put it into a ponytail there asre slivers of white all over. She stated that the scarring was so much that the hair would not ever grow back (making it seem worse than MPB since propecia won't even help one bit) but yea, obviously it will be better for my condition since now I can apply this stuff always with 100 percent contact with the skin.

Like the other guys said, best buzzing it with your own clippers, also before you use them, you probably should get a sharp pair of scissors and cut the pony tail and the rest of your hair down to a suitable level, as it will make buzzing it alot easier .

Also if you do have a rash/bumps be very gentle when you first start to clip it down and also start with a large clipper number and check your head with each length shorter if you do not wish the rash to be visible.

If you do eventually decide to shave with a razor, the shadow look does'nt take long, by the end of the day mine is like that , but of course the no guard buzz may be easier to maintain for that look.

Hope that helps mate.

If you have dark hair, you'll most likely have a good amount of shadow even if you shave with a blade, so I wouldn't rule out taking it down to the skin.  Like anything else, it's all trial and error.  The good news is, you can shave it all off and the stubble grows back very quickly.  You can check the growth from day to day and decide what length suits you best.

I never cut myself without a guard.