The most efficient way to do both is to unlock Qing Yan, the green bird, at level 40 by spending soul essence on talents.

Devil's Covenant is an unlockable scroll that requires killing 50 Desert Boar. It reduces your current health by 75%, similar to when a red chest takes a % of your health, doubles your current copper, and increase future copper gains by 50%. Great for runs to get really high upgrades on your guns.

Air Strike is simply an optional Steam achievement. Kill 5 enemies in a single Leap 50 separate times. Sounds simple until you realise most enemies are pretty spread out and take a lot of setup and luck to actually finish them with leap. Your only real opportunities will be the groups of beetles in stage 1.
I'd advise to kill the beetles with explosive barrels instead until you also have that achievement, since stage 1 is the best place to progress that.

As you progress through the initial stages, you can occasionally use Leap to kill groups of enemies whenever possible. Some ascensions for increased leap radius, cooldown, and defense will be helpful.

Go through Anxi Desert as normal.

Once you reach the boss do NOT fight it. Simply avoid its laser beam attack, usually by standing still until it picks a direction.
Desert boar will begin to periodically spawn. Keep kiting them in circles until they reach clumps of 5 so you can use Leap and kill them all. Make sure you don't have items that passively kill them such as Blazing Hoop. If you do, you can tab into your list of occult scrolls and hold right-click to drop them.

Just keep this up for awhile and you'll easily farm up kicks for Air Strike. Devil's Covenant will unlock much earlier since you'll often kill more than 5 boars at once.

Do note that the summoned lanterns in stage 3 do not count.

Congrats on easily cheesing a long and annoying achievement in your progress toward 100%.
Now you can use the campfire in solo mode and try to farm Lobsters with Fire damage.