Hey Carss, For the 104 it depends on what kind of finish you want. If you are going for that "in the war zone " look, then use the dullcote for the finish, but only spray it one time. This will dull down the decals, and keep some of the bare metal look. Keep in mind that the ground crews for the planes that saw action did not have time to polish up the planes before each flight. If you want that "showroom shine" on the bare metal then use the glosscote. As for how many coats, that up to you. If it looks good after one coat then leave it be. If you think it needs more then hit it again. For the SR-71, and the D-21, Use the dullcote. To fix the mess ups I don't use paint remover. paint remover can eat the plastic, so I don't take the chance. I just sand away the ooops. Start with 800 grit sandpaper, when most of the mess is gone switch to 0000 steelwool then use a good papertowel to polish the plastic. Remember to sand lightly as not to lose any details in the the plastic. This takes some time, but it's better than paint remover distroying your model. One other thing to remember, is to Have fun ! And don't worry about what others think about your work, if your happy with it then that's all that matters, Hope this helps out.
Charley