Nice! I agree with all advice given in regards to no pressure (just skim the top of your skin) and blade experimenting. I have never used your soap but I will say to you what I generally say to new shavers... get yourself an italian soft soap like Cella or Valobra. Italian soap is like training wheels, ridiculously easy to lather, good technique/bad technique it will work. Might be worth a shot, some of the harder soaps can really take time to figure out. Best of luck
It's difficult to pinpoint why you are not getting a good lather with the Van Der Hagan. It's not my soap of choice but I have used it and it lathers up well. My technique is to soak my brush in hot water for about a minute, then lightly shake excess retaining some water in the brush, then swirl the puck with it until the brush picks up a good amount of soap on it, looks sort of thick like paste. Then using a bowl or scuttle that has a small amount (about a tablespoon to start) of hot water in it, I swirl the brush in it and what initially looks like runny suds turns into thicker lather after swirling it for about 30 seconds. What works for me is NOT to have too thick of a lather. In other words, you want it wet enough so that it doesnt run down your face but you also want it to have enough moisture so that your razor glides smoothly while shaving. I do a three pass shave, wtg, xtg, atg without undue pressure on the razor simply reducing the beard little by little with each pass. Derby is not my primary blade but I do use them regularly and they do a fine job on my coarse thick beard. Technique is what you need to work on. The best tip I can offer besides face prep (washing face and a hot towel or hot shower) prior to shaving is learn to keep your wrist locked while using the movement of your arm to move the razor. Keep at it and you will find what works for you.