Thumb Slap Pluck
The thumb slap pluck is most commonly notated as an "X" below a set of notes, where the X indicates the thumb slap and the notes indicate the strings to pick.
The thumb slap pluck is a combination of your regular picking technique with a thumb slap, used to target specific strings.
This technique will be counterintuitive to those who are used to the thumb slap strum technique, as it requires two opposite movements to be done by the same hand.
Thumb slap pluck vs Thumb slap Strum
The thumb slap pluck is a useful alternative to the thumb slap strum when specific strings are to be played during the slap. It is more accurate to thumb slap pluck when targeting specific notes than to thumb slap strum the same notes. Doing a thumb slap pluck on one or two strings sounds very different in tone when compared to a thumb slap strum.
A thumb slap strum's tone is similar to an aggressive downpick while a thumb slap pluck's tone is close to your usual picking tone. A thumb slap pluck also makes controlling dynamics easier and when done right.