Never used a Merkur adjustable, but, based on how I use my Slim, I'd suggest trying a low setting for your first shave, and avoid changing the setting between passes.. I generally prefer to perform my WTG pass on a high setting (7 or 8), then drop-down two notches for the two XTG passes, and, if I feel the need to do any touching-up, I go down another notch. I suspect that my preference for starting on a high setting is due to a combination of heavy beard growth and the relative mildness of Gillette adjustables - if I don't set the razor high enough for the WTG pass, I find I have too much growth remaining for my XTG passes. If I were to try a Merkur adjustable, I'd probably try the opposite approach in order to make best use of the extra bite.