Norwegian Ruck March prep

So my state (I’m national guard) has a Norwegian ruck coming up. I’ve done it once before, but didn’t really train for it outside of like five 10 milers leading up to the event. I passed, but literally with like 30 seconds to spare. Trying to do better this time around.

What are some ruck training tips/techniques yall have used? Specifically I’m looking for strength training I can do that allows me to not have to destroy my knees by rucking twice a week for 7 or 8 miles a piece. Thanks in advance.