Since I've done work for multiple companies now, and they are all basically the same in process, I don't see a problem with answering some questions. It's not like I'm giving away secrets.
The company will usually just give me the hard parts that need paint. If I get any clothing, it's only so I have a reference if I need to color match something like armor to a uniform like with Cobra Viper.
If it's a licensed piece, I usually get or gather references and try to paint as close to screen accurate as I can. If it's more of a company's own take on a given piece, I may get some direction on how they want it to look, but mostly they've all trusted me to "do my thing".
I don't do any paint by numbers type of thing unless I'm trying to teach China some new technique they haven't done yet. Mostly, I just paint, and they figure it out on their own. I'm pretty impressed with their ability to color match.
Figures are easier to paint because all the parts are usually separate. Statues are harder because they are more or less sculpted as one chunk or several large chunks which sometimes need to be assembled and have the joining lines puttied over. Also with statues, different parts are all sculpted together, so they can require a lot of masking to keep colors from bleeding or hazing over onto other parts.
Working time ranges from a week to 2 weeks generally. Some projects have gone longer. This tends to be a very hurry up and wait type of business. Painters are the last in line to work on anything and it's usually up to us to save the day and meet the deadline. Really though, delays happen all along the way and deadlines are deadlines until they aren't met, and stuff gets pushed back all the time.
Time between paint and announcement varies. There seems to be no standard. Last year, I finished Boba Fett and Grievous mere weeks before they were shown at Comic Con, but there's been times it seems like a year has gone by before something I painted gets revealed. They don't always get finished in the order they are planned to be revealed. And sometimes, I think, companies want to be sure China can produce it properly before they commit to unveiling it. I've noticed Sideshow has started actually waiting on some pieces til they have solid China samples to show as the product instead of the prototypes. You guys have never seen my prototypes for the Battle Droids and STAPs. You'll probably never see my Grievous again either.
I think that about answers your questions.