I got a little carried away when I was writing this guide and forgot that we were talking about private mines. I wrote this guide for public mines, so there are parts which private mine owners can skip.
An easy way to safely transport large amouts of resources from mines and crafting lots of stuff:
1. Set up a base or a safe house right next to the mine. A tent camp will do too, but you might want to have at least a primitive workbench at your disposal. This place will serve as a safe place for crafting and storing your stuff. You can also park your car here safely.
2. Never bring a car to a public location, there is a risk of it getting stolen.
3. Instead, bring a brahmin with you to the mine and let it carry all the resources you / your slaves have mined. Works best in safe mines, where there is low risk of your brahmin getting killed. If you go to an unprotected mine, make sure you look after your brahmin. If I remember correctly, slaves have limited carry weight, so they are not as efficient as brahmins when it comes to transporting large amounts of stuff.
4. Use the brahmin to transport the stuff to a base / tent that is close by. Never travel long distances on the worldmap with a loaded brahmin, they die easily and you'll lose the resources. It is best to tell your brahmin to stay close and run away from all encounters.
5. You can tell your brahmin to drop all stuff via dialogue. This is especially useful if it is standing right next to a workbench.
6. You can pick up all items from a hex you are standing on by using the shortcut CTRL + G, so pick up all the gazillion ores and minerals and start crafting. Sure you can't move because you are so seriously overweight, but it doesn't matter if you are already standing next to a workbench. This eliminates the need to constantly grab more resources from the brahmin during crafting.
7. In case you need to, you can drop all items from your inventory using the shortcut CTRL + D
8. You can alternatively load the materials into a car and then haul them to another place. Just do as above, tell your brahmin to drop all items next to a car, pick them up and then put them in the trunk.
9. Drive to another location and bring the brahmin with you in order to move the resources from the trunk to a container or a workbench.
10. Never bring a heavily loaded brahmin to an unguarded town.
As you see, this method eliminates a big part of walking back and forth when mining and crafting and allows you to have lots of resources in your inventory when you begin crafting.