Hey Froggy62,
There are lots of great theory lessons on this site and they have their place. However, if you've been blowin' the blues for 35 years all you need to do (IMO) is pick that guitar up and play bro. There are only 5 or 6 notes you need and you more than likely know them. I appreciate good harp music so if you've got some to share please post it. Take care Froggy62.
Doug