I see you fly from time to time, imho it's easiest way.
Find some 2-4BR aircraft that can be used in attacking ground targets and do some Air RB. On majority of maps you will find a plenty of soft targets - focus on them. Best, if they are a little away from center of the map.
Check your inventory - if you have wager, use it. If you have order for most destroyed ground targets, use it during battle. Do not activate order from the start, be sure to be the winner. If you notice map with big number of soft targets, fly towards them. If you do not see anyone close to you, activate order and start destroying targets. In majority of battles all players will be focused on dogfights or chasing bombers - that's your chance for SL in big numbers.
When you search for proper aircraft, be sure to check SL gain % on stats card. If you have any low rank premium aircraft - most probably that will be your machine for SL.
...
Read more