Equipment: I have ProTaper Pillow Top grips and wear Fox Polar Paw gloves. I would get a raw right thumb after a day of hard riding my 2004 YZ125 on trails and the track.
I bought these donuts to see if they helped - they are definitely the answer as I have not had a problem with raw thumbs at all. I might dab a drop of superglue between the donut and the grip to keep them from folding over, but it's not really a problem.
Highly recommended if you suffer from Raw Thumb Syndrome.