Place towels to fill oil return holes. Dropping a keeper and not finding it is a problem. I have used the air method and a tool similar to the one Mancini sells. I can say I have learned something here today I have thought about every time I have put a spring compressor on a valve held up by air and the piston at the bottom of the stroke. I would like to here more about puttin the string in the cylinder to support the valves.