I should have taken pictures as I did it, but I didn't and now you really can't see anything.
But it's easy to try for yourself.
1. With the brake lever down (released) wiggle it side to side and listen for a rattle. Also run the shift lever side to side with and without pressing on the side of the lever to see if there's a rattle when you aren't pressing on the lever.
2. If it is, you can try to see if it goes away by stuffing the space between the lever and the base. I took the heat shrink tubing and fished it under the lever from the back side with the lever completely released. Keep pressing it in until it stops, then lift the handle a little and the tube will go a little further.
3. Put the lever in the down position so the brake is completely released and try to make it rattle again.
4. If the rattle goes away, you can do the same thing but put some RTV on the tube to hold it in position permanently.
5. One rattle Gone. 99 left to go.