I have heard good things about Loural Mountain Forge's Gun Browning and Degreaser. As it is a degreaser, it is (supposedly) more forgiving of oil contamination. Anyway, I plan on using it, but won't start until I finish up refinishing the wood on a marlin 39m (a couple days now). Even then, I will be polishing the rust out of the old Iver Johnson.
And, since my eyes are always bigger than my stomach, I just bought a Colt 1903 for a follow up project.
I've heard the same about the Laurel Mountain product. I never used it mainly due to cost. Although, thinking about how much acetone, de-natured alcohol, and rubber gloves I've gone through, it's probably at best, a wash.
I love those 1903's and have thought of getting one of those as a project as well. Are you planning to put a high polish on it? It could just be a myth about rust bluing not working as well with highly polished metal, but that's what's always given me pause about re-finishing a Colt - doing it justice with a high polish.
However, the more I do these rust blues, the more I'm convinced that the process imparts much more depth to a 'matte' finish than does regular hot salt bluing.
I'm looking forward to seeing the results of your Iver Johnson and that Colt. Good Luck!