Here is a quick progress update.
The external tanks have had their decals added. I started with the black stripe that starts at the forward black stripe and then spirals around to the back of the tank. The two tanks do not have the same spiral. The white tank has a spiral that goes from the top front around the tank and back to the black end also near the top. The silver tank spiral starts at the same place as the white one, but the spiral ends at the back near the bottom instead. Then there a LOT of info and warning placards on the tanks. There are eight on the front of each tank under the nose. Then there are four on top of the tank. Fourteen on the outside of each tank. Two on the inside of each tank. Five at the back of each tank. Finally there is one on the pylon of each tank. I then put on a light coat of matte clear to protect them.
The next thing up for them is to thread the piping on and through stand-offs. But now it is time to start painting the X-15 itself. I started by painting an area of Vallejo White from the ventral stabilizer and up to the nose gear door. Then another white area from wing tip to wing tip near the flap hinge line.

I then masked off exactly where I needed the white stripes to go. I used 1/8 inch wide tape for the wingtip to wingtip stripe and two strips of 6mm tape slightly overlapped for the stripe from the ventral fin to the nose gear door.
With that done I sprayed the model with a base coat of Tamiya NATO Black.

Now I need to let the paint cure for a couple of days before I mask off for the areas that will be painted with Vallejo Black Gray. That should give me time to get the external tanks all piped up.
Thanks for looking. More to come.