Are there any resources I can consult to aid me in getting better at land navigation?

I’m good at measuring distance, four digit grid coordinates, and six digit grid coordinates. I am having trouble with 8 digit grid coordinates and want to get better. I have been trying to practice on the U.S Army Future Soldier site, but I’m still having trouble grasping it. If anyone could give me some advice and nudge me in the right direction, that would be great! Thank you. I am using a 1:50,000 scale military map as provided by the Future Soldier site with a coordinate scale and protractor.