You want to use chalk pastels. Rub them on some fine sandpaper fo make a little pile of dust to apply with brushes, Q-tips etc. I personally have had little success with oil pastels for anything.
paint
future ( 3 of coats as needed)
decals
future
washes to accentuate detail
flat coat ( or gloss/semi-gloss)
NOW the pastels
Is the general order of things