My primary language was COMPASS, the Assembly Language on Control Data Mainframes. I supported the COBOL and Fortran compilers as part of my job as a Operating Systems programmer. Now I use C and Java mostly with a little bit of Fortran.
The teaching part came in when my company brought in a bunch of university students as interns (co-ops). The ones that got sent to the MIS department had to learn COBOL. The math and science interns used Fortran, and my buddy taught that. Back in those days you could look at a dump and debug a program rather quickly. I swear my boss could look at a dump and reconstruct the Fortran code.
I've written little BASIC programs without an interactive debugger--I mean, it was an Apple II after all--but I can't imagine having to write any serious software today without a debugger. I have tremendous respect for those who did. It feels like I'm cheating somehow. :-)