plz go for someone who know how to adjust rear wheel alignment which is done in conjunction with front wheel.
generally its straight forward task as compared to front wheel alignment but i believe it has certain parameters which are different from front wheels alignment.
i would suggest to get the data from online manuals and then compare with what the alignment shop is doing.
P.S. in Lahore, i have been visiting a guy for 20 years, once he disclosed that most alignment guys rely on the steel guage and level guage to do alignment and camber etc. Sensors and computers are used for customer satisfaction mostly.