RemOil is a lubricant, not a solvent do it will not hurt the finish at all. Hoppe's 9 is a standard and hard to go wrong. I use it occasionally. I typically use Butch's Bore Shine for my solvent. It won't hurt your finish either. I only use RemOil as a rust preventer. It can gum up if left in little crevices. I use Breakfree CLP as a lube. Then before I put the gun back in the safe, I hit it with a misting of RemOil on the outside to keep an corrosion away.
Let us know how the STX does. I hear those are great guns!