Lots of hard work. I remember crying (yep, crying) when trying to do my first PFD screen, not fully understanding gauge logic.
I am basically a one man company now. Every now and then, someone will voluteer and help out, paid of course, but most of it now is all inhouse by me. That is a overly huge undertaking with planes like the Learjet was, which took 'over' a year to make. With the Lear, it had in-model coding, and systems coding for effects. The switches and engine management were hardest. Fuel systems work different then FS base code works, so that had to be worked out and was tremendously difficult.
I use Photoshop CS, 3DS Max 2014, the P3D SDK to export models, and it has taken me years to learn how I do all of this.
What I would do if I were you, is start making things in Gmax. Its free. You can export to FSX easily. Learn to make a coded gauge or see if someone will make them for you. Not many people can. You need to learn how to code animations for models as well. You'll need to learn how to make things exactly to scale, perfectly to scale, or people notice the odd measuring and shape issues and will steer clear of your plane just because of photos. Its a massive road. But, if you start simple and 'learn' the basics, you will get there.
If you have lots of money, you can hire people to do the work for you, creating a dream team of sorts and getting the team working well on a plane. You can buy models online, then have a person set it up for FSX, another person paint it, another person create the airfiles, another create the gauges. But....... With the money you spend having all this work done, you then need to recoup your input. With me, on the Lear, it was a flop. Very low sales. People didnt read the manual, they didnt know you CANNOT start a plane cold and dark with a different planes save point that was shut down, so that screwed up their start-ups with it. So a year of hard hard work was nearly for nothing.
So, you might just start out simple, create a freeware plane, launch it, deal with public inputs, reviews, complaints, see if you can handle that, and start moving forward from there.
