Tattoos over scar tissue

Sorry if I am repeating a previous question but I could not really find any postings about this. If possible, how difficult is it to tattoo over scar tissue? As well, is there anything I can do to make tattooing over these scars any easier (i.e. creams, lotions, etc.) Thank you.

Hey guys, I'd like to know the answer to that as well. Got about a 13 inch scar on my left side from a martial arts accident where ultimately half of a lung was removed. The memories of that accident and the pain from that time have often left me wondering about tattooing over all the scars. Though I earned them, they are not necessarily all that attractive. I know so what. But......