Hi Rich,
Earlier this year I set up a walking/hiking Facebook group called Lost in Pace. I initially started the group not because I actually had group members but because colleagues and friends found out I love walking and hiking. They made comments like 'I wish I could do that' or 'how do you do it?' 'where do you go?' and so I simply set up 'Lost in Pace'.
I'm by no means an expert at Facebook and setting up the group was very easy. I put up a disclaimer/rules. Basically it says, things like no advertising, add only your photos, wear appropriate walking or hiking footwear, carry your own first aid kit, water and snacks. Walking poles are optional and bring your mobile phone. Also that I will wait only 10 minutes if you are late but then will leave.
When I put up an "Event" on Lost in Pace I put a meeting point, time and map. I include a brief description of the walk/hike and approximate duration. Sometimes I haven't actually done a particular hike before, but I just let them know and don't sweat it if I get briefly lost. It's all part of the adventure.
So, when people made those comments again about wishing they could do it, I basically told them if they wish it then make it happen. Join the group and come along. So what started with one is now about 50 members. Not all 50 come along, but there is a core group of about 15 that come along when I do a hike. I've found that there are a those that love getting outdoors and enjoy a good hike and those that enjoy belonging to a Facebook group, seeing the photos and hearing the feedback but they just haven't got to the 'action' stage. Either way, it surprised me with the speed and numbers of people that want to join.
So while I haven't set up a Camino forum, perhaps a little of my experience in setting up a group may be of use to you.
Set up your forum and see what happens.