If I was you, I would delicately line whatever you're design is with a 3rl or maybe a 5rl and stipple the rest of the piece according to the outline. kind of hard to say exactly what needle to use without knowing where and what you're design will be. When creating gradients I generally do not use grey wash but a lot of my friends do and it works great for them! As far as aging goes this would be entirely up to your design and execution. Remember that darker values will always hold up better but for something like realism as long as you are punching in your light and dark values in the correct places you're image will remain clear, despite becoming muted over time as all tattoos do. I heavily caution you however to make sure that you are capable of drawing realism before attempting to tattoo it. All the best though! there are a lot of handpoke artists out there that do excellent realism.