After you hotbox it make sure you let the smoke out completely or else it tends to just smell bad... especially if it was boxed with a blunt. It depends on how much you smoke, the size of your car, whether the interior is cloth or leather, etc.
Are you only boxing it once? How much are you planning on smoking? How long are you planning on keeping the car boxed?
after you let all the smoke out, drive it around with all the windows down and spray some frebreeze. the smell will be gone in less than 30 minutes.
If you do this make sure you dont have any weed or paraphernalia with you because the smell might be enough for probable cause (i cant remember if the SC had a case like that or not but it still should be taken into account).