“Indicating to pass” is insane and needs to stop
I live in an area in regional Victoria where you’ll get behind one of these guys for a 5-10km stretch.
And I grew up in regional NSW where it could be more like 15-20km.
If you’re on the asphalt you overtake if you can see it’s safe to do so as usual, or if the operator can clearly gesture to you, unmistakably, with a hand signal that it’s safe to go around.
I’ve never heard of the right turn signal thing.
I’m in rural sa and many trucks will indicate to let the person behind know it’s clear, especially over a crest.
I’ve seen it a few times when travelling. I think that the best way for a slow vehicle to indicate that it is safe to overtake is to indicate left (near-side, passenger-side, kerb/shoulder-side, whatever) and merge onto the shoulder. This is what the majority of tractors do in my local region.
This provides those following better visibility of the road ahead and allows them to make up their own mind.
Also, those following, just be patient. The only reason why the tractor would be deliberately driving slow to annoy you is because you a being a dickhead. Don’t be a dickhead on the road.