What I recommend is that you just do it the normal way which is covering in bondo and then sanding. However there was one piece that I covered in cheesecloth and then in bondo, witch did seem to work well, but was rather unnecessary to do it like that, but since the piece was already covered in the cheesecloth I tried it. At first I like this because spackle is much easier to sand than bondo, but the problem is that spack cracks very easy, so I do not recommend this method. Then I covered the cheesecloth with spackle. I took layers of cheesecloth and glued them on by mixing glue and water and brushing it on.

For this step I tried using a different method which really didn't work as well as I had hoped.