Given Dimitri's nature i've always viewed him as someone who dabbled in kickboxing, specifically the more aggressive aspects of it that involve dominating one's opponent and forcing them to either defend or fight on your terms, seeing as Kassy is a different type of person,  perhaps he taught Kassy to play more to the defensive aspects of guarding and dodging whilst waiting for the enemy to expend their own energy before laying into them? It'd have a nice little balance going between the two.