I've tried it hot while running, and it didn't work for me.
What works great is hot not running and turn the engine over by hand with the fan, don't waste the time pulling the plugs, you only need to make two revolutions, it's not that hard.
It's been a couple years now, but last time I adjusted the valves on my 1 ton was at a rest area in Washington state in the middle of a road trip, only takes 10 or 15 minutes.
-Get your 5/8" wrench, straight screwdriver, and two feeler gauges ready.
-Go for a ride and get the engine up to temperature.
-Stop and pull the valve cover.
-Turn the engine until you see the exhaust valve close and the intake immediately open for any one cylinder.
-If that happened to be on the #1 cylinder, then adjust the valves on the #6 cylinder. Or # 2 goes with #5, and #3 with #4.
-Continue to turn the engine till the valves just close and open on the next cylinder, and adjust the opposite/corresponding valves. This can all be done within 2 revolutions on a 4 cycle engine.
This works because when a cylinder is alternating from exhaust stroke to intake stroke, as easily seen by the valves, then the opposite cylinder is close to TDC on the compression stroke, it's lifters are on the base circle of the cam lobes, and the valves can be adjusted.
For most any engine with an even number of cylinders this works. To determine what cylinder pairs with which take the firing order, for our 6 cylinder it is 1-5-3-6-2-4. Write the numbers down in order in two columns, first the left one with the first half the numbers, then the right one.
1-6
5-2
3-4
This shows you which pair of cylinders you can adjust the valves by watching them move on one cylinder and adjusting the other set.
Grigg
P.S. When you put your valve cover gasket on use gasket adhesive, contact cement, or weatherstrip adhesive to stick it only to the valve cover, put nothing on the other side (although some folks like wheel bearing grease). Then when you adjust the valves it's easy to get the cover off and is reusable as is.
