I bought a similar kit from Smooth-On to make casting of Warhammer 40k miniatures. It was amazed at the detail and accuracy of what I created!
The secret was using a back massager to vibrate the table to get out the bubbles!
Artisan Alliance made a couple of very good videos on high detail resin casting with silicone molds [1]. They focus on mechanical keyboard keycaps, but the same ideas apply to many other things.
I’ve done it for making fake ancient coins - like another responder, I used a Smooth-On kit and it couldn’t have been easier. Though I was casting bismuth alloy rather than resin. One tip, be sure to dust the mold with talc to allow air to escape. Also the vibration table tip sounds good.
Might be better with just 3D printing, body filler and spray paint.