Three times. Twice through the suit, once on bare skin.
It takes time to figure out exactly how gentle you should be - even if you are gentle, you still might tick them off.
I was about to go out of town for two weeks last June, so I asked my friend to feed the bees while I was gone. I invited him over so that I could show him how (you use sugar water). Now, I have a full bee suit and a half of one that covers the top of the body plus your head. I let him wear the full one, and I wore the half suit, but I wore shorts that day - bad idea! Everything went pretty well at first until I took off the inner cover and set it down on the ground. I had only been keeping bees for a month at this point, so I didn't yet understand that slower movements are the way to go. So when I set the inner cover on the ground, not as gently as I should have, they got MAD. About 5 seconds later, one of them stung me on the shin. When a bee stings you, they release an alarm pheromone that tells other bees to go after you too. You can use a smoker to mask the pheromone, but I was being an idiot and didn't think to light it and bring it out there with me. Not wanting to get stung by more bees, I ran a little bit away, scraped out the stinger, and yelled over to my friend the instructions for how to feed them.
That wasn't very smart on my part ;)