If you don´t have an extra fridge for brumation like me, do you have a cool place in a cellar?
Constant temperature between 5° and 10°C is elementary for hibernation of most Garter Snakes.
Excuse me, but which specy do you want to brumate?
I let my snakes have at least one week in thier enclosures to digest after the last meal.
Then I put them into a tube (Faunabox) for further one or two days in my livingroom (= snake room).
Next step is storing the snakes in the tube in my cellar at about 15°C or one week. Then they´ll spend minimum one month in my hibernaculum fridge before warming up is vice versa to the procedure above.