Yup just 1 or 2 chunks for the whole cook. You can add the 2nd after the 1st is done although I'm not convinced it matters. A bag of chunks should last you many cooks. If thats not enough smoke flavor for you, add one or two more next time.
Here's my kettle setup for smoking. I put down a good amount of unlit coals, with a couple wood chunks in the pile, and then pour on maybe 15 lit coals. Catch the temperature on the way up and bring the intake down to a very small opening. Try to keep the lid closed as much as possible to not feed the fire. You can't control the fire if the kettle isn't kept sealed up.
I think you're probably just laying on the smoke too thick though. I promise you'll taste lots of smoke flavor with 1-2 fist sized chunks. :becky: You might want to add another chunk or two in the future, but you'll wind up with a butt that you won't want to throw out on the first time around.