Turning on the water after draining the pipes

I had an upstairs shower valve solder leak after the faucet burped when I turned the water back on. I shut the valve off before I turned the water back on so when the water ran through it there was a sputter of air then water came out (then the pinhole leak). After a plumbing repair do you guys leave the faucets on and turn the water on slowly to avoid this or was it just a fluke?

Not only do I turn it on slowly but I also leave at leat one faucet open so it can not reach max pressure until I slowly cut the other faucet(s) off. That banging action of water hitting the pipes can definitely damage weak spots and faucet washers as well as toilet valves.

Turning water back on slowly is a good idea but the leak was caused by a poor solder job..
It had nothing to do with how the water was turned on.
The joint would have leaked anyway...

Good call on the bad solder job. It turned out the pipe wasn't in the valve all the way when it was soldered. I still cringe every time I have shut off the main to drain down the pipes. So should I leave a few open and pressure those up shut the main back off and redo the rest?

That depends on your confidence in your solder joints. You'll have to call that shot. If you are confident in your ability to visually evaluate solder joints then you should do so and act accordingly. Ideally, you could pressurize with air to at least 90 psi and look for a drop in pressure after a few minutes. It should hold about 90 psi without dropping for at least 15-20 minutes. As I said, water banging in the pipes will break weak joints that otherwise could last as long as long as the house. Of course, a good solder joint will hold an enormous amount of abuse. Unfortunately, not all soldering is done under perfect conditions so there will be failures from time to time.

turn on

A good system does not care how fast or slow you turn the water on. If you have a bad joint and it leaks because you turned the water on too fast, you are lucky, because it would have leaked eventually. Probably after you repaired the wall, and then tiled it.

Actually I was changing out the valve cartridge in a 30 year old townhouse shower and noticed the leak starting on the joint through the escuchen hole (thank God) after the water burped out. But it was a faulty soldered joint, I can't believe it made it 30 yrs. I have heard horror stories on the repair bill on a very slow leak over time behind the wall on a shower valve.