How to restore jailbroke iphone 6 to about to be jailbroken iPhone 6+ with a different iOS?

[musicnet356]

I've backed up my jailbroken iPhone 6 running iOS 8.1.1 to my Mac using iTunes. I want my new unbroken iPhone 6+ running iOS 8.4 to be setup the same way. Do I first jailbreak the phone, install my Cydia apps, and then use iTunes to restore from my iPhone 6 backup,

or do I first restore from backup my 6+ using iTunes to my 6 backup on the Mac and afterwards jailbreak my 6+ and lastly install my desired Cydia apps?

 

[kch50428]

If you have iOS 8.4.1 on the 6+ - you're outta luck as 8.4.1 eliminates the currently used vulnerabilities and makes jailbreaking no longer possible.