its not hard or complicated.
nor do u need air.
if u want to use air, great. if not, use clean thin nylon rope. take out the spark plugs and feed the rope into teh cylinder while the piston is at tdc.
the rope will keep the valve from falling into the cylinder whilst you take apart the valvetrain and do the seals, etc. i'd replace the valve springs while u r in there. you'd be surprised how much top end can go away with soft springs, adn they're cheap.