The orange material is Modeling Clay similar to Super Sculpey & has to be oven-baked to dry, harden & can be sanded, however, primer has to be layed-on quite thick before spraying on colors. The yellow-ish material is Tamiya Epoxy Putty. Minute, finer details could not be captured (probably didn't press it down hard enough) such as the embossed
Brembo font on the disc brakes. For mould release, grease was brushed-on.
This isn't really casting, more like replicating using
finger-pressure & suitable for small parts, saw it in a Mecha forum & gave it a go. 2-part liquid resin would still be ideal & less of a hassle IMHO. hth

edit: spelling.