Thanks to this thread I just did this quickly and easily. Silicone tubing from the aquarium department at PetSmart, $3.50. Additional weight for each pot: less than 2g.
I left the tubing off the bottom of the handles, where they receive the most heat and won't touch your fingers when handling. I think this will be good especially for alcohol stoves that you can't just reach down and turn off when the boil is reached. Nice to grab it off the heat quickly.

The MSR Titan Kettle handles came off easily and when reinstalling they resumed their original shape on their own. The tubing went on very easily with just water as lubricant.
The SnowPeak 450 mug handles were thicker so the tubing took a little more elbow grease but still went on in just a few minutes with only water as a lubricant. The 450 handles needed to be bent a little back into their original shape, but that was easy. I used two sets of pliers and a cloth (so as not to scratch) to bend the original bends in the handles a little more and they went back into their original positions easily.
Another tip for handles that can't be removed: moldable silicone glue called Sugru. Available in many colors, cures in 24 hours into hard rubber that resists heat up to over 300 degrees. Also great for fixes around the house. Excellent stuff!