I didn't see this section before I posted my home made flares, but here's what I've done to make my own fiber glass flares. https://www.rx7club.com/old-school-other-rotary-63/my-never-ending-project-784050/
What you'll need to form the flares
1. floral foam you can can get them at your local art stores
2. Glue gun
4. sanding block and sand paper
Fiber glass supply http://www.fibreglast.com/
1. Vinyl ester resin I use 2gal for mine this comes with a hardener
2. Fiberglass mat...this comes in different weight
3. Release film
4. Measuring cup
5. Acetone for cleaning up
You dont have to use a weave mat for this, stranded mat works great to build up the flares. about 3 to 4 layer will be more than enough.
The first set of pictures (from the link)are how I glued the foam into the fenders.
Once that's done use a knife to shape the flares, a long skinny knife works great.
Then to smooth it out using the sanding block.
You dont have to use the dry wall mud on top of the foam this get real messy, you can apply the resin on top of the foam. Some foam will melt once the resin apply so make sure you use the green floral foam.
spray the release agent on the around the fender and let dry. At this point you can apply the fiber glass resin, once dry you can use a plastic putty knife to fry loose the flares. Now when you remove the fiber glass flare off the fender the foam will come out with it. I find it easier to remove as much foam as you can then use a high pressure hose to remove all that's left off. Just use a cut off wheel or a dremel to cut out he excess materials.