My Sears compression tester came with the facility to add air to the cylinder like you need. You need about 80 psi and any small compressor would be ok. Beg, steal or borrow one!
You will need a valve spring compressor too.
Did you read our recent thread on this job, as we did it 2 weeks ago?
Here is the link.
http://www.peachparts.com/shopforum/showthread.php?t=168126
On our 300TE, we had to remove the radiator to get at the 27mm nut on the front of the crankshaft to turn the engine and then to lock it in place against the frame rail when we were working on the valve seals.
Oh, one thing you MUST do is when you get the rocker shafts off, before trying to compress the spring, get a socket big enough to fit over the keeper and give each valve a deft smack with a mallet. The caps are well stuck on the valve keepers or collets and all you will do is release the air in the cylinder! You will hear when they loosen.