Justin is a disciple of Johnny Bush. You may not know Johnny, he's in his 80s now, his big national hit was Whiskey River, which he wrote. It was later a hit for Willie Nelson. Johnny cut his teeth in Ray Price's band in the 60s.
Justin did start playing early, but IMHO a lot of it comes from being born blind. My late friend Phil Parr was the same way. Flawless bass playing and singing no matter how much the bass lines varied from the vocals. It's like an extra sense in lieu of blindness.
YT seems to be down right now or I'd post some videos. In the meantime, you can see some of his basses in his
photo gallery. Note the rmute in some of the pics. When he's playing bass in FB videos, it's usually the Ric or the Eko.