There has been some interest in the fine art of playing with epoxy, so I thought I would add some helpful hints;
Have all of your materials ready before you mix the epoxy. Once mixed, your working time is limited. Depending on temperature, it has a "pot life" of about 15 min. and a "working time" of about 30 min. It cures faster in hot weather, slower in cold. Materials you should have on hand are
-Mixing pots (the plastic ones, like for paint)
-Mixing sticks - I get the ones made for epoxy (black) 'cause you can reuse them a few times.
-Disposable Nitrile gloves (lots) - Harbor Freight has a box of 100 for about $6.00
-Disposable chip brushes - box of 50 (1") at HF for $3.00
-Fiberglass (cut to size before mixing)
-Thickener - I use West Systems 404 or 406 (high density adhesive fillers) for most of my work
-Acetone - Nasty stuff, but crucial for surface preparation.
-Chemical gloves - the nitrile gloves don't hold up to acetone, and it can destroy your liver.
(My liver needs all the breaks it can get)
I start with surface prep. Rust areas are de-rusted, then all areas that will touch epoxy get wiped down with acetone. When my repair area is clean and dry, I mix about 3 pumps of epoxy in a cup and stir thoroughly. To this first batch I add thickener to make the mix 'peanut butter' consistency. This is sloppy enough to still stick to stuff, but firm enough to hold its shape. I use a mixing stick to mash this into any holes/voids/uneven areas to make a semi-smooth surface for the fiberglass.
When I've used all the thickened epoxy, I mix another 3 pumps in the same pot. I use a brush to spread unthickened epoxy on the areas to be fiber glassed. Then I start adding fiberglass (you cut it to size already, right? the clock is ticking now.) Smallest pieces go on first. Apply fiberglass and press gently into the repair area. Use the brush to "wet out" the fiberglass, applying epoxy and smooshing it around until the fiberglass turns from white to clear. Add the next, larger layer of fiberglass, and repeat "wetting out". Add as many layers as you need to fill the hole or bond stuff together. I always finish with woven 'cloth' fiberglass because it gives a smoother finish once it hardens. If you do lots of layers, it's a good idea to get a resin roller and roll over it to mash out air bubbles and extra epoxy. No air bubbles=a much stronger repair.
Clean up spillage with acetone before it hardens, or better yet, protect surrounding surfaces before you get started. Epoxy sticks to ANYTHING and the only way to get it off once it hardens is sanding or grinding. Set the pot and mixing stick aside and let them cure. If you squeeze the pot and bend the stick once the epoxy is hard (the next day) it pops off and you can reuse the pot and stick (see picture, the brush is in a perfect epoxy mold of the pot).
I used about 4 layers of fiberglass to bond the floor to the walls. In the picture above you can see the pre-cut fiberglass layers for a large hole on the floor. Seven was just about right for that.
Once you finish the repair and it hardens, you can sand it and 'fair' it if you care what it looks like. (I'll go into fairing another time, it's a process unto itself) All fiberglass repairs should be painted or protected from sunlight. It is technically a plastic, and will start to break down with exposure to UV in sunlight.
Wearing a bandanna is a good idea if you have hair. I got epoxy in my bangs while working on the boat in Key West. Nothing to do but cut it out. So I had a nice little duck's ass curl in the middle of my forehead, and everybody laughed at me for a while. Fairly warned be ye, says I.