You could get a label maker:) really though, does consistency matter? I would think a doctors signature would be great- the more illegible the better. If you are worried about a legacy, maybe you could also print your name on the back, very clearly?
I notice on some prints, even on 10.4 mil paper, the signiature will show through if it is held up to the light.. If viewing normally it cant be seen and assuming it would be framed it wouldnt be an issue.