
How about something like:
"Hi, my name is XXX and I'm calling to ask if you would consider taking on an apprentice for work experience. I am interested in becoming a groomer but want to get hands on experience before paying for grooming college. I don't have any experience in grooming but am willing to work hard and without pay if given the chance. I do have experience in handling and training dogs and have XX of my own. (expand on your experience)."
I think I would probably go in person and start by asking if this was a good time to talk to the manager. If not ask when they would have 5 minutes free and say you're happy to come back when it's convenient. People aren't really that scary once you start talking to them. I've never once had anyone bite me :) The worst that could happen is they say no. So what, just say thanks for listening and ask someone else. You'll get there.