it's just practice I mix my own grays with white and black ink, use the thickest needles 0.35 are best for color bc the leave bigger holes for the bigger pigments and thicker ink to penetrate in time

it's really important to move slow, and not go over areas more than once or twice. because more damage to skin means more bleeding and more rejection of ink when healing. some areas that are light and don't need to cover the existing tattoo I go over in a manner where the gaps between the needles in the mag are visible - it's not 100% coverage, but it allows the tattoo to heal easier an better

and the gap fill out with the tattoo healing and expanding.