I'm not familiar w/ GT85, but, like Rem Oil, it look like it's just a lubricant. LINK
/ I use various lubricants to lubricate and protect the metal surfaces, but not for cleaning. If you're looking for a single product to "clean, lubricate and protect", tow such products I use are Break-Free CLP or Eze-Ox.
What part of your gun are you cleaning? If your cleaning the bore, toothpaste is actually not too bad as it's a mild abrasive. If you use toothpaste, I'd use some dry patches and wet patches (lubricant would be ok) to clean the abrasive out of the bore.