I never received formal training, but since one of my father of one of my mates was the Support Company Sargeant Major...
And our own company SgtMaj was an old machinegunner himself....
Well, lets just say informal opportunities to learn new things came along on a regular basis.
There's nothing as much fun as a 100 round burst from a tripod - except maybe a few hundred kilos of ANFO loaded into an old car body...

Car? What car?