Duck Park club race track was made entirely with BTB and one or more X-packs from this community. To use, unzip folder to your \rFactor\GameData\Locations directory.
I do not know how to use 3d software, but I'm able to play with BTB and be able to make race tracks. Thanks Brendon!
Here's a lap of my track as exported by rFactor's replay fridge:
I'd like to have some track-side stuff, but I don't model, and I haven't seen items I like in xpacks I have, so it's just a bare race track right now.