As for Gay, Frank Reese did mostly outcross on his female line throughout the 50s and 60s. He mostly used brace-bred field champions such as FC. Williams' Pointline Buddy (sire of Gay Baker and Gay Dash) and FC. Wilson's Timmy II (same hound used by Tom Dornin). It would be a stretch to call his methods line breeding. He never bred to FC. Dingus Macrae, to my knowledge, but did breed to a dog called Dutch Fork Huntmaster, who was a full brother to Dingus and owned by someone in the Carolinas near where Frank lived. From Huntmaster, he got Gay Blaze.
After Frank's hounds got popular in the 1970s and 80s, he started crossing more and more on his own males, thereby starting to linebreed and inbreed. This strengthened his bloodline and fixed many of the traits the Gay line is known for. I would guess much of the reason for his change in breeding style was the lack of good outside lines, since the brace hounds were useless by then and the gundog movement was barely started. Frank did breed once to Little Ireland's Binkey. From that cross came Gay Time, who occasionally shows up in pedigrees today. I watched Time run several times and liked him, except that he would run his mouth in the check area when he should have been quiet. He searched like a bird dog, and many of the hounds from Baker were the same way. Quick, active, always moving out ahead of the handler.
As for outcrossing....Once you have built your bloodline, outcrossing should only be done when you need to add something to your line, such as conformation, mouth, size, etc. Then you have to go right back to your own line in the next cross, or you run the risk of losing your original traits/line. Most of the crosses a breeder makes should be within his/her own line, and not outcrosses. As your hounds become more and more suitable to you, it will get harder and harder to find outcrosses that you believe will help you. That is why you see most of the well-known breeders using their own studs more often as time goes on.