Like robotprops says, just take your time and, wherever you can, work out what you're going to do before you do it... just as you're doing. In all the time I've been building and painting models and props (in my rather amateur way) the times it's gone really wrong is when my impatience has made me rush into doing stuff without double checking my references or fully thinking through what I'm doing. Still catches me out to this day! But I'm better at pausing and thinking than I was! You're doing all the right things so far.This can be a bit of a rabbit whole. Budget, time,knowledge and ability are major factors in my progress.
You guys are so skilled, knowledgeable and experienced that I am apprehensive in my end result as I have a lot to live up to. I am also apprehensive in the painting of this pistol as I know it can either make or break this project.
As far as the painting goes, if you're at all unsure about colour or finish for a part, don't jump right into painting straight onto the part itself. As you say, that can 'make or break' (although there's not much that you can't recover from if you do 'break'... it's usually just the time and frustration to strip everything back and start again). I always keep scrap pieces of resin so that I can use them as test pieces for paint finishes - go through all the steps you're planning to go through on them rather than the actual kit part(s). That way, if something is going to go south it won't matter as it's on a thrwaway item anyway. And if it goes OK you've got the confidence to do it again for real!
Based on what you've posted so far, I'm really looking forward to seeing your progress!
As for your colour choices above, they look good, and pretty much match the preliminary colours I'd planned when I come to do mine. I'm going to use Alclad lacquers, I think - Stainless Steel for the Bulldog frame, trigger guard, triggers, barrel and the 'post', Gunmetal for the Bulldog 'inner' grip frame with heavy weathering back to stainless steel around the edges, Steel for the receiver and bolt handle assembly, Polished Aluminium for the butt plate and either Polished Aluminium or Stainless Steel for the inner bolt. The outer grip frame with be gloss black with weathering back to Stainless Steel. All the covers, the sight, clip housing etc. will be either gloss black or satin black.
I'm slowly prepping my kit parts for fit and pre-primer finish at the moment, but major work on this kit is waiting until I finish another (TipTop/Anders P) project that's intervened in the meantime. It's all but finished - just waiting for a replacement part from eBay. Teaser below!