There's a lot of different techniques people use for tech hit. Some people just slide a finger/knuckle around all 6 buttons. Double piano works. You don't have to start with lk if it uncomfortable, sequence doesn't matter to much really. I sometimes accidentally dark force when starting on lk.
Lk,Lp,Mp,HP,Hk,MP is generally considered optimal but kinda funky to pull off, practice doing 4 input piano lk, lp, mp, hp and once you can do that try hiting hk with your pinky then back to mk with your ring finger. Most people online only do 4 input tech hit anyway, adding in the 5th and 6th once they can do that consistently. A good way to practice if you have an 8 button stick is to assign one of the 4th buttons to a P2 attack that hits multiple times like leilei's hp. Press that button, and you have a long window to put your self into block stun to practice. (also why you avoid moves like that in normal play)