This is what I have used for quite a few years, works good covers can-bus and more it's more than just diagnostics.
http://diag4bike.actia.cz/en/homepage/
How about the one that is in your head, many seem to overlook this tool.
When properly applied it provides very useful solutions and innovative answers, however as with many other tools, when abused it results in poor performance.
Give a think to using tractor paint ( tractor supply or other places ).
I painted the shop sign ( all metal ) about 7yrs ago and no rust at all anywhere.
Applied with roller and paint brush.
Thinned a little for first coat and full strength for second.
If done in a reasonably warm area, paint...