Okay-I have a question about this pixelation problem.

When you go into your brushes, do you use the shortcut key or choose the actual brush from the drop down menu?  In Photoshop it is the ctrl B to bring up the brush sets.

I ask because when you use that shortcut key option, Photoshop automatically brings up your brushes in the "Pencil" selection rather than the "Brush" selection.  When you use brushes in the "Pencil" option-your brushes will come out pixelated like you have shown us in the WIP you posted.

Check your brush- If it's in the Pencil option, simply switch to the Brush instead and try to remake and re-render the tattoo to see if that fixes it.

Sometimes, it's a simple shortcut key that can really mess with you.  It does me. ;)

Oh-I'll post this ...well..everywhere you have the question at just to help you out in not having to hunt down a hint? 

Hug Dar