We recently did a pretty decent sized project for a customer of a 15mm Mexican force for the battle of the Alamo. This is one of those rare occasions where I took the time to take pictures for a hot-to during the process. This is how I generally do 15mm Napoleonics. While this is for the Mexicans at the Alamo, the process will work just fine for French with a few minor modifications.
This isn't the only way to paint Napoleonic French, it is just the way I've found to be easiest to me. Hopefully you can take something useful away from this tutorial if you already do Napoleonics, or if you want to get started on the period this might help you make the leap.
While the uniforms from the period can be complex, the painting process doesn't need to be. I like to break a project down into a manageable process.
First the figures need cleaned and primed. I like to work from a black undercoat, working my way lighter with highlights.
Then I do the pants and small clothes. Since they are white I go with a lighter mid-grey, Cell Vinyl's Grey #7, followed with an overbrush of white.
Next the coats. I used Coat d'Arms Royal blue and applied our own mix of dark blue wash:
Next I work on the muskets. I used Vallejo Beige Brown for the wood since I was going to apply a wash to bring out the details and this would darken things a bit. Then I used GW's Leadbelcher for the metal parts, then applied our Armor wash to the whole gun. This wash is a slightly brownish black wash so it adds a nice shade to the gun, picking out the details.
Next the red bits: collar, lapels (on the figures that have them), cuffs, and turnbacks, and pom-poms:
Now I do the flesh. I know this is backwards from how many people paint their figures; ie, do the flesh first. Since I tend to paint sloppy first, cleaning things up more and more to the end, I find it easier to do the flesh toward the end, cutting in on those parts. That way I don't have to worry about getting other colors on the flesh while either dry-brushing or washing.
For these I used P3's Ryn flesh (which I transferred to a dropper bottle which I prefer) washed with our own flesh wash. Our flesh wash is a close clone of the older GW flesh wash so that would work fine. If they were 28's I'd worry about trying to make the flesh more "Mexican" but in 15mm I think the distinction is really lost.
Now I do the black bits, like the bayonet scabbard, cleaning up the yellow bands on the shako, etc, and for the Mexicans their sandals.
Then I painted on the green tips on the pom-poms. These figures from Blue Moon were kind of unusual. The pom-poms kind of looked like plums, but kind of like pom poms, but kind of like cockades. I wasn't really pleased with that but I went ahead and did them all as best I could as pom poms:
Last two steps were to highlight the black bits with a bit of dark grey, then the gold bits such as the shako plate (which really lacked definition on these figures), and the tips of the bayonet scabbards.
That's generally how I do 15mm Napoleonics. Your mileage may vary, however. I tend to paint sloppy-to-neat; in other words, I to the things that are either sloppier or that I don't have to be as careful with first, working cleaner and neater as I go. That way I don't have to worry as much about getting paint on things that have been done until I get toward the end of the process. It is just easier and quicker for me to paint this way. If you are the type of person that needs to see immediate results or must always keep things very tidy that method of painting may not work out for you as the figure doesn't start looking more like the finished project until almost at the end of the process.