I came back to Combat Arms from a 700 day break exactly. I'm rusty and low on GP so I want to power level on Death Row. I'm assuming it still works so please if you are interest add "Antoz" (no quotations). I don't know if nexon has patched it and there's a new method of power leveling but I always used to do this. If you have elite mod then you host. I'm really just doing it for money cause I'm broke as f*ck.
If you want good EXP/GP, just do Arms Race. (Espically when there's an EXP/GP event.) Also, there's always 100% on a map that's won every weekend, be sure to check the main page and their forums for the winner. Refer here for more info, I assume they'll be doing it until they run out of maps.