Its hard to do because CA will always close on your 2nd or 3rd scan. Its easier if you have a lot of GP to start with. Say 23k or so. You need a hexa converter. Change ur GP to hex and scan CA. Extract the packets and freeze them. Then edit them as hex values. (Put 999999999 and convert to hex). Unfreeze them. Then scan at the normal value. (23000) Scan in 2, 4, 8 bytes as seperate scans. Freezing all data packets of equal value and changing the values. Its easier if you can make a trainer to do it because it faster. These are done consecutively.
Same to change your rank except Nexon I think keeps a record of your rank so it will soon change back though you can still access the Kilo or Recruit server depending on how you changed your exp.