Around here RLO ends up black usually, BLO fares a little better. You can kick it a little harder with japan dryer, that's basically more of the metals and whatever nasties they use to "boil" it.
I kinda like danish oil with Waterlox over it, which is really just hand rubbed cut varnish. Easy to repair, poly is a bit tougher and tougher to repair.
I've had close calls with rags too, homeowners are the most casual. I've had to be pretty blunt with our current clients a couple of times when they have "helped" over the weekend and left rags inside. We typically take em out and torch them at the end of the day just to be done with the potential.
