For B+G, it appears to be completely random. While mashing *might* increase the chances for more hits, it hasn't been consistent enough for me to feel that it does. Plus I've gotten a high amount of spanks plenty of times without any mashing at all. But I suppose it doesn't hurt to mash anyways just incase.
As for his PB A+G/B+G/B, while just mashing directions increases the hits, mashing everything increases it even more. However, the opponent can simply counter mash with directionals only to minimize the hits.
Lastly his third mashable move is his side throw where he stomps on you for a while. Normally after the animation he falls into Poker Bluff, but if you mash directionals (seems to work better if u just mash everything) he will land on his feet and in a better wakeup position. There's a downside to this though; a break window opens up during the stomping animation in which the opponent can press A or B (depending on what the throw was done with) which will allow them to escape.
I actually discovered this a long time ago on the PSP version. And when I met Dampierre's creator/SCV Director Daishi Odashima last year, I showed it to him because I thought it was a glitch. However SCV got released, and even 3 patches later and it's still there. Which is odd because that break window mechanic doesn't make any sense and seems glitchy.
