Yep, good advice so far. A few other things to add:
1. Be cautious if you are 'wet' sanding. I've found that this 'softens' the future and can sometimes make it turn 'milky' It will generally go away after another coat, but it can be horrifying to see it happen when you're not expecting.
2. You *could* strip the future altogether (with alcohol or ammonia or windex), but you'll have to assess the paint to determine whether or not this will affect it as well.
3. Be careful when sanding so that you don't go through the future and into the paint. You probably need to concentrate your sanding mostly in the areas of the 'runs' and just do a light overall sanding on the areas that orange-peeled.
4. I've also that when I put future on, the first few coats look fairly pebbly and like orange-peel. However, after I get a few of those base coats on, I apply a more 'wet' coat and then just set it aside to dry. This usually levels right out and takes the orange-peel away entirely.
Good luck.
M.