If you have actual razor burn, you need a barrier on your skin, because the barrier that was meant to be there has been taken away. The skin drying out is one of the things that causes redness and pain.
One thing that I find helps is using witch hazel + cocoa butter. I use a solid block of the stuff.
I use Aloe Vera gel for pre -shave because it is know to help improve hydration. Major cartridge MFG's use it on the lube strips so that should convince some folks.
Aloe Vera Gel is used for Sun burns because it cools and relieves the drama and works for razor burns also. Very rare I get razor burn but there are Newbies are looking for solutions when they get them.