I'm not a fan of poisons as predators and scavengers eat the dead or dying rodents and get the poison themselves. In an enclosed area like the passenger compartment, I'll scatter several Bounce Fabric Softener sheets. Mice go more by smell than vision and it hits them like a hammer. Stick your nose in a box and take a deep sniff and you'll see what I mean.
On the exhaust, steel wool stuffed in there does the trick.
On wires, you can get Bitter Apple at the pet food store. I got a taste of that once and that was all it took.
On mouse traps, the wire spring is the best. You want the ones with curled metal to hold the bat. The flat metal can have the bait eaten and not trip. I use peanut butter as bait and poke it in with a tooth pick. I'll then break the wooden tooth pick off so if the mouse gets the bait, it'll still gnaw on the wooden pick and trip the trap then.
Lastly, a momma cat with kittens will eat any rodents that show up. Plus, kittens are so cute. just get them used to people so they don't go feral.