Yes, Loke taught Jelani a lot. The way Loke had him trained he woulda been a Navy SEAL by 14 (yes, I know I already made that joke).
But when you ask Jelani how he got that good he usually says that his background consists of Enclave, NCR, and The Wilds.
The Wilds in this case is Uthorim. As good as Loke and Jelani are Uthorim rounded up a lot of their training.
He taught the boys about the flora and fauna of the Wasteland, instructed them in medicinal lessons, taught them how to get 100% out of any creature they hunt 'cause it's not just the meat to eat. He taught them how to use the organs and bones, how to skin and tan the hides and fur, something that really benefited Loke as he was already fond of tinkering with armors.
Uth also taught them how to make traps, something both lacked, and he taught them how to track anything or anyone no matter the terrain. This man single handedly turned two very deadly and capable people into rabid bloodhounds and now the Wasteland has to deal with it.













