effort.....start with some 1000 grit wet/dry sand paper, and finesse the finish sanding in ONE direction only....once you have 'killed' the shine, go to 1400-1800 grit, and sand perpendicular to your original line of work....then go to 2400-3000 grit.,.......etc. until you get to 12K (12000 ! ) grit.....by then the paint should make Auto Art blush with shame................gamble is that there is enough paint on the surfaces to tolerate this process. Do NOT 'press' on the sandpaper...let the grit do the work., and you will see that you needn't get 'all' of the orange peel effect off in one grit ....let the process help you.
Oh, and do plan on spending about 3-4 HOURS doing this....wash with plenty of water while sanding....that helps lubricate the surface for a gentler cutting action. I actually put the model into a small plastic tub and sand while it's underwater 1