Ken’s suggestions below are the way to go but something you may want to try is a product called Wire Glue made by Anders Products (www.andersproduct.com). It is essentially a black colored paste that, when dry, has the same physical & electrical properties of electrical solder. If you apply it at your rail joints it should help if not completely solve your conductivity problems without dragging a soldering iron up to the ceiling. I had similar problems on my N scale layout and this product made them go away. Just be careful not to use too much since it dries hard as stone and could cause derailments if over done (as would a metal solder). A little goes a long way.

Hope this helps,

Geof from the US