Good alternative to bondo, apparently. 

Bondo advice from the forums

Advice for sanding, but I don’t have a power sander, so I have to do it all by hand haha

Basic materials list from the forums (different from mine tho haha) 

Here is a visual example of what to do before bondo:

This is good advice if you don’t want to buy chrome or any paint and want a decent shine on your helmet. I’m sure it works for both helmets as well. :]

Visor help from the forums. :]

Help with fiberglass~ (from the forums of course)

Help for making the visor and the LED for Thomas’s helmet (from the forums)

Sanding and primer help (from the forums) 

Vacuum forming information (in case you wanted to make Guy’s helmet too). :]

Another alternative to bondo I suppose, haven’t tried it myself, but could work: “1/2 cup of plaster of paris with 5 tbsps of resin, a small amount of water and catalyze w/e 5 CC = instant bondo putty.”