He meant he got down the mini dash practicing with Houtenjin after 6C CH because if you're not point blank 6Cing someone, Houtenjin won't hit them unless they are big hitbox characters like Tager and Hakumen. As for the maximum damage, j.6D > 66C is actually not the optimal combo with for the following characters I already posted: Ragna, Lambda, Tager, Makoto, Mu, Valkenhayn.
For these characters, you should do j.6D > 66A combo instead and if you already have 100 heat, it nets you 9.4k with optimal starter instead of 8.5k. If you have 50 meter, it gives you more meter in return and still does more damage because you get an extra 5C > 6C rep.