With the pro oil dyes I use a dauber that is very saturated and apply the dye liberally. Usually more than once. The browns and mahoganies may appear blotchy at first but will even out very nicely after allowing it to settle for a couple of days.
I think the problem with the airbrush is that it does not allow enough dye on the surface to really "penetrate" the leather.
IIRC, particle had a similar thread not that long ago. He uses an airbrush also.
As far as the Mop n Glo, I dont know, katsass has used it for years with great success. I dont know how chemically different it is from any of the other water based acrylic sealants.
Having said that, I still use products targeted to the leatherworker.