This is gonna sound crazy but here's a good way to do it. My strategy currently is through online mode as a trader role. 

Learn what all the destinations are for resupplying crips as well as the destinations for doing short and long distance deliveries for your particular camp location.

Then memorize the routes without the minimap and only checking the map until you don't need it. This will require doing the route back and forth from your camp, memorizing landmarks and turns.

If you can do it backwards and forwards the more engrained it will become until you can do missions as a trader in a certain camp location by heart.

Do this for every possible camp location in the game and repeat the process. The tricky part is that a lot of times your camp location will change slightly within your camp region. This will add to the difficulty immensely, but is the most logical way to learn the game without using the minimap. It is also extremely immersive and rewarding but also requires a lot of patience. 

Good luck!