This one uses a balloon, attached to the dipstick tube:
https://www.youtube.com/watch?v=Snepo7rdhsc
This one uses a home made manometer from clear plastic tubing attached to a piece of cardboard so it can be measured, also attached to dipstick tube:
https://www.youtube.com/watch?v=c-ZSnesa-to
You need to measure the difference between idle, and 2000 RPM. Air filter should be clean, or removed.
Cheap and easy ways to tell if you have good ring seal.
You can do compression check, or a leakdown test too, but either of these tests will point you in the right direction for excessive crankcase pressure.