Coug, the best product I've found for rust prevention has been "Eezox".
Available online from the link below. If it's good enough for daily use by hunting guides in central Alaska, it's good enough for me.
I've read so many tests about the efficiency of various oils, etc, and this product consistently comes out on top, or near it. Rem-Oil as you mentioned usually comes out near the bottom, as was my experience also(I've not tried any of their newer stuff).
I would not recommend Eezox for lubrication only.
My safe is in a semi warm spot in my house and I've not had to resort to the de-humidifier products.
http://www.eezox.com/index.htmlGood luck to you.