Baby powder and prayer... having good steel cored levers helps too as many plastic levers are simply unworthy.

Some tyres are just a pita to install... I have some Avocet TT30's which are 27 inch by 7/8 folding tyres and I have never run into a tougher install than these.

They were well worth the pain as they are the best 27 inch racing tyre ever made.

Once they were installed and stretched a little removing and reinstalling them is still a challenge but it's nothing like that initial install.

I always use baby pwder / talc as it does make difficult installs much easier... Schwalbe Marathons can also be a pita.