I just reinforced my set of styrene gauntlets with Fiberglass under the instruction of MARROW_SUN and a friend of min Bobby C. The process worked out great and I would like to share it with you all especially those that have never done FG.
If you have a set of Vacu-formed gauntlets, odds are that they are made from styrene, ABS or sintra and will warp with heat increases so you cannot use a urethane resin for the FG you need to use an Epoxy Resin. Preferably a cold cure but all of them have thermographic properties.
I found a Fiberglass Supply house here in Detroit that I was able to get my supplies from. First, it is important to note that you should score the insides of your gauntlets or"key" them as it is so called with an 80 grit sandpaper before laying the FG.
I used a 1-3 ratio Epoxy that is 1 part hardner to 3 parts resin. I just measured them out in cheap dollar store measuring cups. I mixed them in a large paper cup and used a glue brush which looks like a small paintbrush with a metal handle to paint the epoxy into the inside of the gauntlets. They are cheap. Cost like $1.50 for 5 of them.
Now, you only have about 15 minutes of workable time so you have to be sort of quick. I already had my Fiberglass cloth cut into strips so that I could lay them overtop of the epoxy. You then take the glue brush and sort of use a tapping motion to get the epoxy to soak into the cloth. Paint a little epoxy over the top of the cloth as well making sure you get all the little nooks and crannies. You don't want air bubbles so even after the epoxy sets up in your cup, the epoxy on the cloth will be tacky and still setting. spend the rest of the time tapping down the bubbles with a popsicle stick and or the brush until it sets up. Let them sit overnight so that they are nice and hard and then you can trim it all up.
Hope this helps.
Mine definately exceeded my own expectations and have a slight flex because I only used 1 layer of the cloth.