This question was indirectly embedded within other more general questions I made in this site, for example here and here. But the scope was more general. I would like to do this specific question here ...
I start every exercise with 3 sets of 3 reps, then I add between 1 and 3 reps each workout, so that it takes me very long to achieve 3 sets of 15 reps. Then I increase the load and start again with 3 ...
I am staying away from the "as-much-as-you-can". Now, in the dumbbells part of my workout I simply mimic a linear load progression at fixed number of reps, á la SL5x5. I just use smaller increments ...