how can i replace valve coil with it still in motor

a old trick is to use small rope and push it in to the sparkplug hole till its full, then turn the engine over by hand and push the vavle up and use a valve spring tool remove form autozone should be about 20 bucks . or u can use a spark plug compresion tester remove the one way valve in it and hook it up to some air and the engine will spin over and the air will push the valves up so u can use the tool on them