Carla
I use the "Perfect-It 3000 Extra Cut Compound. Black container with blue stripe on side. # 6060
It will remove scratches 1200 grit or finer in Hard paints.(I actually have used 800 with a DA then 1500 then buff)
I would try an area back on the transom without sanding first. If you feel there is still too much orange peel then use the wet dry 1500-2000 grit. Remember when that boat is in the water you won't see that orange peel so bad as looking down the sides or directly into it. I have not used your Imron and again I don't want to steer you wrong and I be the cause of you repainting
I think there are many fine experienced painters on this forum that can help you. I hope they give ya some pointers.
BTW:I have seen orange peel in many gelcotes on boats out of the factory
