If you're at a game someone else will have a can of propane.
Duster is more expensive, has a lower pressure (less FPS) and over time can screw up your mags. You can use it in a pinch but it's a serious pain to get the gas into the mag.
Just keep an extra can of propane lying around, hell I keep a tank on me in the field. You'll have enough for 100+ pistol mags or 80+ assault Rifle mags.
“We sleep safe in our beds because rough men stand ready in the night to visit violence on those who would do us harm.”
To those Rough men... Thank You.