My advice? Skip hot wheels except for only true mid sized cars, they come out to the correct scale. Smaller cars like a mini from hw works great for 28mm, and a truck for 15mm. For other cars, better to scale, green light is good, had a, and a few others. All cheap and easy to get in the states. For the minis, I'd hit evil bay and look for a deal/lot. Or you can buy from a company like Elhiem. I'd enjoy to seeing your projects too!