grab some high density foam, sandpaper and a some sharp hobby knives and start carving. before computers and 3d printing, all the molds had to be made by hand.
if you have a tallent for that sort of thing thats your best bet, or you can design it in cad and pay a bunch of money for someone to produce it.
vacuum thermoforming is very easy though. just google it. you can build a table for very cheap to do typical rc car lexan. for complex maths and simulation you would want to design it in cad and get it printed on a 3d printer but then you could simulate aerodynamic stuffs.
if all you want to do is make a scale care body, just start carving, sanding, filling, carving some more.
Sanwa M12 - Xray T4/16 - Xray Nt1/16 - CRC XTI-WC - ProAMPS - Hobbywing - ReVTECH - ORCA
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