Watch the Travis Right Thumb online guitar lesson by Gareth Pearson from Travis, Atkins & Reed Guidebook
Probably the most recognizable asset of Merle Travis' guitar playing was his right-hand thumb technique. He made the most incredible beefy, honky tonkin' groove. Muting the strings with the palm of his right-hand, while his thumb pumped the groove, strumming down heavily yet effortlessly.
It's important not to articulate each note. You almost want to brush the strings right on the beat, but because we're muting (or choking, if you will), the sound you're making should come out "chunkier".