Haven’t been able to find the same sign for value? Is there a way to reduce the rust without damaging the remaining paint?

Some guys use the prep and etch chemical from home depot. I haven't used it yet but have used vinegar with some success. I think lemon juice can be used also. Just be gentle, take your time and test a small spot 1st.

So White or cider vinegar? Do you just use a soft cloth dipped in the vinegar and wipe?

I used white vinegar with a clean cloth and used a little until you know how it is working. At least this is a cheap less aggressive method before using other chemicals.

We're you able to clean it up some?

I haven't had time to try. Gone all weekend Walleye fishing.