I'm currently using a small white plastic sheet over the front of the lens (lens set at infinity) to get a uniform exposure. I used to use the grey card method, but find it difficult to get uniform light at times. The plastic sheet is practically foolproof. Ansel Adams talked about a "preexposure device" in The Print. It's just two plastic sheets instead of one with three sides to make a "pocket". Then you can get fancy and use ND gels with cardboard holders to control the light more.
For the measuring I bought a used color densitometer (X-Rite 810) from ebay for about $300US. It's indespensible IMO. Also be sure to buy a plaque and transmission reference. You'll need a way to zero out the unit initially and periodically thereafter. I measure for Zone I by finding the neg with a density between 0.10 and 0.15. When I make the test neg, I use twelve frames like so:
1) Zone I 2) +0.5 3) +1.0 4) +1.5, 5) +2.0, 6) Zone I
7) -0.5 8) -1.0 9) -1.5 10) -2.0 11) blank 12) Zone VIII
substitute 1/3rd stop increments instead of 1/2 if your lens can do that. Develop in you favorite soup (mine is PMK and Paterson FX-50 these days) and measure the negs. After Zone I is nailed, you can vary the dev time to try for Zone VIII (from 1.30 to 1.35). It can be tedious and I have burnt five or more rolls of film testing, but it pays dividends when you get your processing down pat. You will have to repeat the Zone VIII part over if you want to test for N+1 and N-1. I've never done it since it's a little more difficult with roll film, but it should be easy once you have your normal EI and dev time. BTW, the smiley face is supposed to be an eight follwoed by a parenthsis. Foiled by the emoticons... :-\