create weapons enum. Put all your weapons in the enum. You can switch the weapons in enum like this:
This is in characterBP.
next go to anim bp and get this enum by casting to character bp and getting this enum. Create a variable in anim bp. Call it weapons or whatever. Set its type to the weapons enum you created earlier. Drag it out and select set. Setit with enum variable from character bp. It looks like this:
Go to anim graph. Get your enum weapons variable. Drag out a pin and type blend poses enum weapons. Get that node. Right click on it and add pins with all the names of your weapons. Connect state machines. Connect the blend poses by enum with final pose. It will look something like this:
Good luck!