I built sets dressed sets , done get in and get outs (putting a show with its sets lighting sound and the like in, the taking it out at the end of the run).Also rigging lighting & sound in my youth.Though in my case got the first job through a friend who was a sound enginener . After that got lots of work though word of mouth.Hard work doing a good job goes a long way in that line of work.
99% of the people that I came across came from drama schools some got the bug for lighting sound or set making, some like me just knew people.
Doing a course is about your best as opens it can open a lot of avenues.
Though never never do anything thats fx.Most boring job ever, only time I did any fx work was making it rain in a small 30 min play for bbc N.ireland 2 hole day of sitting around and 15 mins work holding a rain bar over the actors heads was driving me mad.Ended up did not even getting a credit on the thing as I was called in at the last minute to help and the boss of the company forgot all about adding my name to the companys fx list
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