hmmmmm. lol. I have blown out thousands of systems,you only need to do it from the clock. But,if you want to do it all three ways,its certainly not going to hurt a thing.
-1st, They really shouldnt leak,or you should not see any water comming out of them.Water may pass through them for a second. If thats what you mean by leak,you are correct. If you are seeing water,thats not really normal.
-2nd There does not need to be any current to manually open/bleed a valve. Valves are basically operated by high and low pressure differences above and below the diaphram. The solenoid and bleeder makes a seal,when you break that seal pressure pops open the diaphram and allows water to pass through,no electricity needed.
-3rd You dont have to,but its a good idea. they are normally closed by tightening,on weathermatic's,the lever should be horizontal to close,and vertical to open. most other valves everything is tight when closed and loose when open/bled.
-4th Wire them up anytime. If you have water to a new valve,they are going to open. if you get a faulty one it may not close.Rain bird DV 100's had a flaw in the o ring that goes on the solenoid,it caused them not to close,thats fixed now. I believe it was a yellow O-Ring,might of been green. If you have one of those that should be the only time youd have any issues,new valves work 99.9999% of the time.
My fault on #1, yes I meant pass through!
Thanks for the info!