Pretty much what Mark says, but I've seen ppl talk about opening up the skin by tattooing with plain water, and then shade.
Also I've seen ppl mention that Bob Tyrrell finishes by tattooing plain water over the whole area, evening it all out.
I never tried these tips myself though, I don't find shading particularly problematic. I think it's a matter of time - if you feel time pressure you don't take the time it takes to do an even shading, which is time consuming.
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