What is the aperture on a magnifier

Don't use a grain sharpener, do it by sight.
My enlarging frame is on the base plate, the negative on the stage.
Search for a section, focus, and open the aperture all the way.
If everything fits, enlarger off, 2 f-stops, paper in, if I have no values, then test strips, develop, look for time out, "sharp" passage.

I have the Profisix and the Lab attachment, but to be honest I haven't used it yet because the operating instructions seemed too incomprehensible to me. Last time I was bored while developing myself to read again, I have to try it out.
Since I don't really care about the paper consumption at the moment, I sometimes make four or five test strips if I'm not so satisfied.
Consider the currently still collect as a craft experience and currently do not have the right to make as much profit as possible right away, but it will certainly change.
If the times get too short, I use the density filter on the Dunco 66 Color and stop fading out to control the times. Allegedly, stopping down 2 f-stops is supposed to bring the best results with most magnifying lenses. Can't test that, but I don't want to know whether 2 or 3 f-stops are optimal. However, stopping down to the maximum is definitely unfavorable, since diffraction effects arise on the diaphragm, which have a visible effect in such a case.

@ Multigrad:
You "need" it for convenient exposure on vario-contrast paper. You know for sure what that is.
The adjustment to the desired gradation of the paper is done by "color filtering". To do this, you can use a color head and look for the corresponding values ​​for the three filter colors according to the table. However, since there is a different density of filters in the beam path depending on the color admixture, the exposure time changes every time. So if you have found a time for gradation 2, but you do not like the result and you want to test four filters, you have to determine a new time. This is not necessary with the multigrad head, since the filters are chosen so that the time remains the same. That was it in the basics. I only have color heads for my two workhorses, but I usually work with fixed gradation anyway, so .....
Hope this statement helps you.

Have fun in the DuKa.
Best wishes
Thomas