Sheltie with haircut too short

Question
Hi,
I have a 10 year old sheltie I recently rescued. I took him to a groomer for a trim before a trip to meet his new family. I asked for a trim ( my mistake and lesson learned). I was not specific enough. When I picked him up, I didn't recognize him. All of his hair had been cut off. His hair is about 1/2 inch on his back and tail and maybe 2 inches on the mane. Could you tell me if the hair will grow back and how long it will take? I worry because of his age. Is there anything I can do to speed up the growth?
Thank you for any advice you can give.
T.

Answer
Oh darn, how disappointing!
Best thing you can do is make sure he has a diet rich in fatty acids - appropriate for his age. As far as  speeding it up all I can say is you can try stimulating his skin with a soft natural bristle brush and gently brush the skin to get the blood flowing which does help to speed things up a bit. However it really will take a while unfortunately, at least 9 months or a year.
Have the dog groomed on a regular basis and avoid the problem you learned the hard way.