this is on your WR450? Run all your carb drain lines into one can and then the radiator overflow into another
If you have the stock coolant reservoir at the back I suspect you're ok with just emptying that out
I used a water bottle for my coolant, just zip tied to the downtube fairly low. I used a purpose made catch can for the carb, also zip tied to the down tube fairly low.
I might have another purpose made catch can, intended to be mounted to the bottom of the swingarm. I'll take a look when loading up Saturday morning.
you can see both of them from my YZ there
on my KTM I guess I'll need to make sure the coolant goes somewhere