Robin, it depends what time you want to spend doing it, and what facilities you have available, such as under cover storage.
If the paint already applied is still in good adhesion, not flaking off, then I would rub it all down using wet and dry to get a very smooth base on which to start the finishing process.
The amount of time and effort put into the preparation is the key to what eventual finish you will achieve.
Once I had a perfect base to work with, then I would use car primer and two part paint, where you apply a base coat followed by a laquer finish, but do not be confused by 2pack paint, where you need a respirator to apply it as it is very toxic!!!!
The paint would have to be applied by spray , which is where you need an indoor area to work.
Another alternative would be Yacht Paint, thinned and sprayed on.