I recently busted through my brick-wall a few weeks ago by reviewing some of my autosonomal genetic matches through FTDNA's Family Finder. Like yourself, my brick-wall involved my great grandfather. I therefore highly suggest that you do some DNA testing, especially autosonomal DNA testing. I believe that the best company avaiable is "Family Tree DNA" (AKA: "FTDNA") and they currently have a special for only $99.00. You can google "Family Tree DNA" to obtain more information. If you do decide to get tested, I highly suggest that you purchase FTDNA's "Family Finder" for only $99.00. FTDNA's "Family Finder" will connect you to all of your cousins and ancestors five or more generations back, assuming, of course, that several of your currenlty living cousins (your distant and unknown cousins) are being tested and are also sharing their list of known ancestral names and/or family trees.
Good luck! If you have any questions, feel free to contact me.
Enrique Treat Gleason