I went to a demonstration in the Koordenwinkel once, at that time I had just started straight razor shaving. It was interesting but not really necessary.

I think an actual course could be useful if
(1) you're a bit afraid of the razor and want to practice in a controlled environment
(2) you've been trying on your own and for some reason things keep going wrong (is it the razor? is it the stropping? is it the technique?)

Not useful at all in the other cases.

An alternative to taking courses is just contacting an SRP/B&B/Coticule.be member in your vicinity and meet up. That's the way I would go about it should I have to start all over.