When I was growing up, my dad used to make a distinction between "parts swappers" and mechanics.
Irregardless of what you are repairing, find out what is wrong that caused the problem in the first place.
You could have a problem in the wiring from the controller to the solenoid. That should be checked with a low voltage detector. There should be around 24vac going to the solenoid. Replacing parts that aren't getting voltage will do no good.
Make sure the valve is open. This is not the same as operating the system. Think of a water spigot with a hose and sprinkler. If the spigot is not turned on, there is no need to work on the sprinkler.
There is usually a way to turn the valve on manually. A small thumbscrew in the top center of the valve should allow you to open the valve and operate that zone individiually.
You may have some dirt in the valve. Most will usually self -flush but it's a possibility.
If the valve is a problem, you can often save a lot of plumbing expense by taking the lid off and replacing the diaphram and re-using the housing. Most installers make no preparation for trouble down the road and when you need to replace the valve, you will also have to replace the connecting plumbing. Which means digging a deeper hole, extra fittings, more labor time, more expense.
In my job in parks maintenance, I have replaced/repaired several zones this year. Some wouldn't turn on, some wouldn't turn off, some were broken by tent stakes driven through the supply line. That was a freak thing, but interesting nontheless. Like I said, find out what is wrong first, then repair.
I have never had to bleed a line to get it to operate. Can't really get my brain around that one. Air locks can cause a problem in a pump, but... I usually flush them during installation or after repairs to remove any dirt that can clog a head, but that's not really the same thing as you are talking about.
From scratch, I would:
1. Make sure the valve is turned on.
2. Try to activate the zone manually.
3. Make sure the solenoid is getting voltage.
4. Check that the controller is sending voltage to the solenoid.
If it's worth doing, it's worth doing right. If you wouldn't put your name on it, it ain't done right!