After you apply dura glas you probably want to sand it starting with 40, then move up to 180, then maybe 800 to get it smooth. Then you can use more filler if you still have large cracks/ bumps. Then sand it smooth again and use spot filler (evercoat is good, you can find it at a boat store) Then make sure its very smooth, spray high build/sandable primer maybe 2 coats. Check to make sure it is perfectly smooth then sand with 800 or 1000 and paint it!
for the skeleton frame, you use probably a jigsaw if you dont have actual table equipment. If youre making MDF rings, you can use a router with a circle jig or a jigsaw, but the router will make perfect circles. When you stretch the fleece, make sure its as tight as you can get it so there are as few wrinkles as possible. This makes it easier to finish.
#1 Rule: Plan, and take your time!! Test fit alot.
You can get by with simple tools. A jigsaw for cutting out the skeleton and a circular saw is nice for big pieces but not necessary. I would highly recommend a pneumatic stapler for attaching your mold material though as it will make life much easier.
I usually use 60 grit to get the shape you want and make sure everything is level. Once you have everything leveled out good you may want to go to 120 grit. This will remove sanding marks from the 60 grit. Once I get the surface smooth I use a guide coat to expose any small dips or high spots. Once those spots are taken care of you don't need to work up to anything more than 400 before primer. If you use 800 or 1000 as mentioned above the paint wont have anything to stick to. Once the primer is laid down you can wet sand that with 400 until smooth and then lay the paint. I'm not a painter but I have built many boxes and that has always worked for me.
Here's one trick i learned from my dad when painting and how to get a smooth even primer coat.
First take just a regular ole spray can , preferably a very dark color. Black, brown, red, green all work fine just something that contrasts the primer.
Spray a very light mist over the entire primer coat.
You should have little spots everywhere not a whole lot of paint.
Sand your primer down everywhere until you can't see the spots anymore. This should leave you with an even-sanded primer coat which is important when spraying your next layers of the the desired finishing color.