We'll need number of cards you have, who they're issued by, credit limits and balance, original loan balance.
Paying down utilization is the quickest way. If you can do AZEO, that would be ideal. Depending on how many cards you have, that would probably net you the most points. Only drawback is it would take about 2 months for the AZEO score boost to kick in. First month is waiting for all the balances to report, second is to take care of the trailing interest and wait for that to report. Depending on the lender, you could ask for them to report off cycle to speed up the process a bit, but we're talking maybe shaving a couple to 3 weeks off depending on when statements cut.
Alternatively, you could pay down the loan to below 8.9% remaining for maximum boost on that, then wait for it to update, or ask them to report off cycle.
The credit cards would be best because there's more moving parts that can give you FICOs, like individual utilization, aggregate utilization, number of cards carrying a balance, etc.
My question is what type of vehicle are you interested in and are you planning on bringing your own financing to the table?! If you were looking to see what Navy can offer you can pay more towards the Loan and save a little 2k or so for the DP (depending on what they need and what vehicle you are looking into), but if you were looking to do a Promotional Finance (which I do recommend over leasing unless you trade out a lot like every 1 to 2 years) then you may need a larger DP depending on if you have any vehicle history or if they offer programs to help with DP or FTB etc. 
