DJ, there's plenty of ways to skin that cat. =]
I've actually got a Corsair on the bench right now and hopefully soon I'll be able to move on to painting where I'll outline my steps for painting and weathering for this particular bird. To start it's important to have all your seams cleaned up and all the particulars of your aircraft ready for paint. Select a primer that you can use with your airbrush as it I find it offers you much more control over some rattle can. Once your primer is down it's time to make some decisions.
How much weathering and where? Your subject is the Corsair so you could get as dirty as you want to and it would always look the part. Typical bare metal spots that stood out along the carb intakes and forward part of the wing where hoses and tools would drag across the surface of panels and rivets. Also, the wing walk, foot holds, and access panel covers were high traffic areas.
After your primer has dried, lay down your aluminum color. There's plenty of paints out there nowadays. Some are lacquer based and some are acrylic. Easy learning curve for all of them. Now that your base color of aluminum is on, it's time for a few quick blasts of hairspray. Practice on a piece of cardboard or whatever you have handy first to note the spray diameter and amount that will come out when spraying. You really want just a thin coat that evenly spreads across the surface. It's possible to get it on the first swipe depending on the can. Allow it to dry and have your aircraft primer color ready. This was typically a zinc chromate green which varied a bit but was generally a yellow-green color. Spray that down next over the main areas you intend to do the majority of your chipping. Once it's dried have yourself a few items to be dressed for success.
Small cup/bowl of water and a wide brush.
Toothpick.
Q tip.
I'd keep it simple for your first time out the gate. That's really all you need. Start by softening the yellow-green color by loading a brush with water and brushing it over the surface of your wing in smooth even strokes. The Q tip is to help with any mess you might be making unintentionally. Let it set up for a moment and then start to test it with the toothpick. The toothpick is small enough to get into little spots but blunt enough to keep from scratching your surface. Begin removing the yellow-green a little at a time. Don't rush. Move it around a bit and don't over work one spot. The thing to keep in mind is you want to leave behind the yellow-green you want to show. Consider the places you want the yellow-green to hang out and the shapes it might take along different panels. You'll be removing a fair amount of this color so just don't rush. If you need to spread more water do so carefully. You don't want to lift all the color at once and ruin what you specifically worked. Once you've got something you like, seal it away in a flat coat. The matte texture of a flat coat will allow for more paint to be received next. Spray your next color once that has dried and when you're ready to return to chipping start the process again. That's basically all there is to it. Plenty of room for the next steps that unfolds depending on how you address your insignia and other markings but that's a good place to stop for now.
Painting either the blue-grey over light-grey or the tricolor scheme is all accomplished the same really. I like to start with the lower surface first. When you move up the fuselage side with it, creep up a little higher so you have a bit of overlap. Depending on how good you are with your airbrush you can get in there with a fairly tight line that will appeared feathered already. If you want something tighter than that, blue tac or Tamiya tape with the edges pulled up a bit will work to keep a soft transition line. (Edit- adding this part as I'm realizing I didn't answer a part of your second concern. I had a couple of distractions running around the house.) To handle removing the darker Sea Blue to reveal what was under it, you're really repeating much of the same steps as listed above. One caveat I'd mention is this. When you're painting the lighter blue across the middle portions of the fuselage you want to get whatever character you want it to have (i.e. splotches, uneven color) and lock it away with a flat coat. That way when you're ready for your hairspray you won't run the risk of over doing anything and chipping through your light blue. Spray your hairspray next. Then the darker Sea Blue. Then load a brush with water same as before to soften it where I assume you'll be adding fuel spills. With either a Q tip or thin brush head (filbert works well) run it down the fuselage to the wing and at somewhat a backwards angle. Try to be deliberate about this and don't pick at it too much. Plan your strokes ahead. When you're happy with what you've got, allow everything to dry thoroughly. You can come back to touch up your paint around your new weathered fuel stains afterwards and seal all of it away in a clear coat to start your decals and whatever wash you'll put down if that's next, or come back with a semi-flat coat for extra weathering with oils and the like. Don't add more steps than you need. If your coats of paint and sealers are too thick, it's possible you may see around a decal where a step becomes noticeable. Handy tip to keep in mind.
It you have any questions about that don't be afraid to ask or drop me a line in the messages. Good luck. Looking forward to seeing what you do.