Pistolero
It depends on the condition of the metal and wood. If you have a lot of loose rust to remove, I'd not go more aggressive than WD40 and burlap, or Kroil and burlap. If you have mostly good blue, all you need is gun oil and cotton cloth, or maybe a lighter oil and cotton cloth. This will remove dirt and gunk while preserving the finish. If it's really dirty, rub it down with Hoppe's to clean. I wouldn't use any chemical more aggressive than this.
Oil the stock with boiled Linseed oil, a coat or two until it stops absorbing it.