This is a quick and easy way to get the 30 "ghost" defeats you need to evolve a Charcadet.

• Find a friend (or a second account on a second phone)

• Friend creates a battle party in "master league".

  The party is composed of the three *weakest* (fewest HP) ghosts they have.
  (On the lower right of the "Pokemon" screen, click on the button and chose HP to sort by, tap again if needed sort in ascending order)

  I label the party "weak ghosts".
  
  

  In this case, my friend's 'mons were 53, 253, and 51 CP and about 10 HP each.
  Note: their CP is irrelevant, because they will *not* be attacking you!

• Select a Charcadet to be your buddy.

  (Choose a Charcadet you want to evolve :)

  You do *NOT* need to "walk" with it (i.e., no need to feed it three simple berries or one gold berry or one poffin).
  
  

  Mine has no defeats yet
  
  

  Scroll down to see the defeat information (click on the down arrow next to "Adventure together" to see the evolve criteria)
  
  

• Select a friend to battle (on home screen, tap on your picture icon, select 'friends')
  
  

• Invite them to battle (tap on 'Battle')
  
  

• Choose Master League
  
  

  (The league doesn't really matter, but 'Master' lets you choose any 'mon to use against your friend.)

• Let's Battle!
  
  

• Choose your party
  
  

  I chose a pre-created battle party that I use against team leaders and Giovanni, but you're going up against the weakest 'mon possible, so just about anything you choose will work!

• About to battle
  
  

• The first battle
  
  

  NOTE: your friend does *NOT* attack you!

  One tap killed, er, "cause to faint", my friend's 'mon.

  Note: avoid tapping directly on the attack circle, because you don't want to waste your (and your friend's) time by accidentally triggering a charged attack!

  Note: make sure your friend is paying attention...when the first 'mon faints, the friend will be asked to choose a second 'mon. (The choice will be made for them after awhile, but ... why wait?)

• The next battle
  
  

  (There is no picture of the third, because I tapped so quickly that the third fainted immediately : )

• You won!
  
  

At this point, click 'rematch' and repeat 9 more times (for a total of 10 battles, which means 30 defeats of a ghost).

I exited after the first battle to show the effectiveness:

The entire process is extremely quick!

Note: the same technique can be used for research tasks that require you to do "10 supereffective charged attacks". For those, I have my friend choose Snorlax, and I choose three mon with quick charging fighting attacks (like "Counter").