Doing nitrous (AkA hippie crack) is hazardous to your health whether you inhale straight from the cracker thing or use something like a balloon as a buffer. But, since we're on the subject...
Doing nitrous from a balloon is certainly the most common method but not the only (or even the best) one. You may also use a refillable whipped cream canister available at any kitchen/cooking needs store (your granny may already have one, as may your work if you work at a bake shop.)
This is what the capsules of nitrous were actually made for; to add that burst of aerosol needed to create and properly expel the whipped cream from its scratch ingredients when the trigger is pulled.
Since we are not making whipped cream here, dont' bother to add any ingredients into the container. Snap the nitrous cartridge thingie into place and stick the applicator between your tightly closed lips.
Breath out heavily and then inhale slowly and as deeply as possible while pressing the trigger. You'll get a huge gust of cold nitrous right down into your lungs; hold it there as long as you can before exhaling. You will start feeling wonderously fucked up even as you're holding that first hit in; be prepared to enjoy this euphoric feeling for all of 30 seconds.
Don't forget to utter a few words during the short-lived peak of the experience, your nitrous enhanced cartoon-like voice is an added treat not to be missed.
As disgusting as you know this is, one hit is never enough. Accept the fact that you'll probably continue these steps until all of your cartridges are laying empty and even then you'll wish you had more.