Once you are comfortable with the number of layers you have applied and the strength of your enclosure it is time for body filler. You will have to use your own judgment in deciding with which type of body filler to start with. In the most extreme cases you will have to do multiple coats with Duraglass just to get the shape and curves under control. I like to sand the early coats with a 40 or 60 grit flap wheel on a grinder focusing on the general curves. Whether you are painting, or covering the enclosure with some sort of fabric you need to get it completely finished to the 36 or 40 grit sandpaper stage. Once again focus on the general shapes and curves being certain they are as you want them. When you are at that stage you could wrap the enclosure with vinyl or another fabric and call it quits. I may do an addendum later describing that procedure and the products I've found that are easiest to use to that end. If you are planning on painting the finished project you are now ready to apply the base primer if you have it. Brushing or spraying the base primer on will basically allow you to skip from 36 or 40 grit all the way to 80 or 100 grit sandpaper. Once you have used it I assure you that you will never go back to working your tail off applying coat after coat of "finishing" filler and sanding with 60 or 80 grit (but if you don't have base primer you'll have to do exactly that). Once you get to 100 grit you can use regular sand-able primer rather than body filler between bouts with the sandpaper. I don't do my own finish paint work, but in general I try to finish everything to 220 grit before turning it over to whoever is doing the painting.