All former
easy ways were of the milking kind - gunning down or resupplying strats.
This easy way is a thing of the past now, with most options left you are in danger of having to meet the enemy
But one of the
quickest way left is still (despite it's recently lowered ENY) upping a Wirbelwind on a base under attack, particularly a vulched airfield. For example, with an average perk modifier, each landed kill of a P-51 or Spit XVI will give you 3 points.