Used task manager to fire up WRT and run Geek Uninstaller. Then use task manager to open Regedit and do a quick seek and destroy anything I found.
Then from WRT run Bleachbit and CCleaner.
Reboot, run task manager again, find win 10 setup and away we go.
WRT has a Antivirus removal tool built in that removes about 40? AV's, including Avast.
It will also scan for leftovers from other AV's that may have been missed from previous uninstalls.