As said before, it depends on how you define a downswing. I think that a
"downswing" is commonly defined as a run of bad luck over a long period
of time which results in a player loosing money while playing +EV.
"(long-term) Tilt" is defined as loss of control over your game which results in the player playing -EV but not seeing his mistakes or not being able to correct them. This, of course, only applies to players who usually (while not tilting) play much better. Therefore a donk playing -EV is still a donk.
So talkign about downswings: there is only one way to get over them: continue playing. HOWEVER, even a minor downswing can cause a major tilt, which will burn your whole bankroll.
If you think you can beat a downswing by playing fake money, you should also consider life sacrifice to Holy Random. That might help.
IF you want to cure a tilt by playing fake money, that's very unlikely to help you as you will have no incentive to improve your game
1) Because you won't be loosing anything.
2) YOu'll be winning more games due to very low skill of fake money players.