Resleeving valve guides

[fiero4819]

I have a 1991 190e 2.6. I've seen in a number of posts that it's relatively easy to resleeve the valve guides. What's the process? Particularly if there's a way to do it without removing the head. I seem to recall there's a way to do it by pressurizing the cylinders so the valves don't fall in.

Thanks