This is how I do it with iD and Relatify:
- Create all the bus stops in iD (that includes the bus stop sign location, and (importantly!) the bus stopping location on the road)
- Create a relation using iD using only the first two or three bus stops.
- Use Relatify to finish connecting the rest of the stops.
Where I live, there is a random collection of buses, all privately operated, with no route maps, no website, and no head office.