We use paper over the board. There is a wide aperature 2' grid screen about 2 inches in front of the plate. You clip your paper on the grid. Draw a cross with a dot on it with a sharpie, and shoot. If you want you can take the paper(s) home and compare the patterns.
Any old cheap bulk grease will work. Most places I've been to use a paint brush to smooth it out.
The local Ikes uses paint and it builds up after a period of time and gets hard to fill the previous shot marks. Besides grease is faster and if you want to change it just use a putty knife to scrape if off.