Tip: Always write over things you don't want seen in the same color they were originally written in, if you can't completely redact it. This fucks with our brain's ability to distinguish a pattern, which is all reading really is anyway.
or, you know, just put a black bar over it so the information is just completely gone from the image?
scribbling over is never going to actually work, the information is still there for anyone who wants to extract it. It's like shouting over someone instead of just getting them to shut up.