pain during BM/ 5 yr shitzu

Question
5 yr old female shitzu.  She was yelping during her BMs and obviously was hurting while pooping.  Took her to the Vet, they cleared her anal sacks, there was a bit of a infection. Dog was given medicine, dog completed the meds (10 days, 1 pill a day). Seemed to clear things up, but it has been less than a month and she has yelped a few times over the past week.  (dog will see a vet soon)
1~ What do you think?
2~ She is probably over fed, could this hurt her when pooping?
3~ A dog that has had one sack infection likely to have another infection in the future?
4~I have seen a pretty poor video demonstration of clearing a dogs anal sacks on youtube. Do you know of another video demo I could find on the web that may be more helpful?

Answer
1) Yes, she could have impacted anal glands that need to be cleared, or given an antibiotic to help a possible infection.
2) Yes, if she is overfed and she is not drinking enough water this could produce large BMS that are painful, especially to a tender anal gland. I recomend giving her a scoop of canned pumpkin pie filling to help ease her a bit. It will shoot things right out.
3) Yes, a dog that has had an anal gland infection is prone to getting it again. I would have them expressed regularly.
4) No, I didnt see a video anywhere. However, here is a great diagram I have sent to people many times. http://www.lowchensaustralia.com/HEALTH/analsac.htm

Good luck!