To get some DMs, try to gather momentum, for example, when kicking, bringing the leg you kick with forward and the other one to the back, the kick will be much more powerful, be cause it doesn't have to share power with both legs. Also I find that throwing your arms in the opposite direction that you are kicking (example do a kick while you are twisting left and bring your arms to the right) adds a lot of momentum and the kick becomes more powerful.
Also when I kick with my foot and the joint won't DM, I try to kick with the part between the knee and the ankle, and most of the times I get 2-3 DMs.
Relaxing always helps me with momentum. I have the habit of, when making a replay, for no reason I do relax all and I obligate myself to continue with most of the joints relaxed.
When you kick, you do contract knee -> extend knee? I find that if I relax the knee, and when the leg is close to uke I extend it, I get DMs more easily.
Sometimes when I am doing a replay, I kick and get no DMs, because I had contracted my hips before I extended the knee. Usually I relax the hips and when my leg gets a little closer to uke I contract it, because when you kick, the kick will have the power of your knee extended + the power of your hip contracting. If you contract your hip too soon, you only get your knee's power.