Which should come first - Rejuvapen or TCA peel? How long in between?

TCA peels are good in certain instances, but not replaced by microneedling.  I personally think they have been replaced by fractional lasers (fraxel) and fractional radiofrequency (viva).  Microneedling should be what you do in between TCA peels or you can combine this with fractional energy devices.  Combining with PRP gives even better results.  I suggest seeing a cosmetic dermatologist with experience in lasers and combination therapies.  Best, Dr. Emer.

Micro-needling motorized devices are basically the same.  Variables include the number of needles per head piece, the depth of needling and the speed setting.  Adding platelet rich plasma to the skin prior to the procedure should improve results.  Several sessions (usually more than two) are required to produce noticeable results albeit subtle. 
Different degrees of acne scarring require more aggressive treatments which may include but are not limited to resurfacing LASER, radio-frequency treatments, fat, Bellafill, Sculptra injections and the gold standard fo patients who are willing to undergo several days of redness (Dermabrasion or Phenol peel). TCA peels may result in mild to moderate degrees of improvement for acne scarring
More than one treatment modality is typically required to obtain significant improvement in acne scarring.
Please consult in person with an experienced Board Certified Plastic Surgeon prior to making treatment decisions.