I can point you in a direction, but a guide I cannot really offer. I think if you are willing to invest some development time, you need to start by setting up your own small openrouteservice instance. As ORS is in some ways an extension of Graphhopper (GH), you will need this one as well.
The basics of what you want to achieve can be done like this (from a quick look into it):
The tags from the OSM file are read in the
if (!relation.isMetaRelation() && relation.hasTag("type", "route"))
This will call the
encodingManager, which will be the
BikeFlagEncoder. In this one, you will have to translate the relations that compromise the
cycle_network types into values for ways. This might be a bit complicated. The basic problem is that as far as I can tell, the tag you are looking for is a
relation, but we need the tag to be applied for all the
ways that it corresponds to.
Afterwards, you can add the tag to the
preferHighwayTag field in the
This will make cycleways preferred, in the same way as residential roads etc are preferred.
If you want even “more” preferred, you will need to create an additional category like the
preferHighwayTag and then assign it a preference value in
I am aware that this is not an easy and quick process, sadly.
Let me know if you need some additional help.