Green’s Dictionary of Slang

bagging n.3

also doing the bag
[bag v. (7) + sfx -ing; the pouring of the inhalant into a bag before use]

(drugs) using an inhalant for ‘recreational’ purposes.

[US]J. Lansdale Rumble Tumble 171: He sniffs a little paint with thinner. They used to call it doing the bag.
[US]ONDCP Street Terms 2: Bagging — Using inhalants.