I'm trying to rack my brain as to how I got this to work, it was my go-to when they deployed the killswitch and it's been working ever since so I can't quite recall how I set it up but I don't think it was difficult. Looking at my extensions I just have Flash 32.0.0.371 but I don't think I had to do anything fancy to get it installed. I'm still using Win7 though so this might be different for someone using an OS made prior to 2007 idk. Come back tomorrow when I've sobered up and had time to look at this if you haven't figured it out yourself.
It's worth the fight, god bless /f/ fuck adobe to death

Here's q quick guide from the top of my mind for the millionth time:
1. Download Palemoon. Install it or use the non-install standalone executable, so you don't even need to give up your chromium needs.
2. Install the latest flash plugin from the internet archive:
https://archive.org/details/flash-player-32.0.465
3. Download the swfchan modded plugins to remove the killswitch
swfchan.com/end
Alternatively if you're hyper paranoid you can also just install official version 371 instead (last one before killswitch)
4. Replace the dll files in your windows folder(s) with the swfchan ones
If you're on standalone palemoon also copy the plugin files in the Lib\Mozilla\Plugins folder of your palemoon root folder
5. use flash
6. ???
7. profit

There're some tweaks you can do afterwards to even further your setup, but that's all it takes.
Palemoon runs all old mozilla plugins and most addons. Important extensions like scriptblocker or scriptmonkey are custom palemoon addons even.