I was joking about the Salmon Leaping Skill. I know that in all liklehood the specific techniques in the Tain are made up (because it was copied after hundreds of years of being passed down orally). However, certain aspects of the book most likely do have historical correlatives, such as there being warriors who taught other warriors martial arts. Nora Chadwick's book 'The Celts' does talk a little (wish it was more) about this aspect of Celtic society.
"Seek not to follow in the footsteps of the men of old; seek what they sought."