@Irish Don’t worry about brushing after the oj. Just keep a bottle of water bedside along with the oj, and after the o.j., just take a swig of water, swish it around and swallow it or spit it out.
What you are trying to do is neutralize the pH in your mouth after the acid from the o.j., and flush away any dissolved sugars that may be left over. The biofilm that you try to clear away when you brush will not be affected by the o.j. to make it more damaging.