Samus has other options like Z-air (hits through and deactivates Gunmen), bombs (which flip cans the opposite way), and obviously uncharged shots.
Generally you want to be the one who stays in control of your projectiles. Meaning if anyone even comes close to outgunning you (can be with as little as a single good projectile, like Greninja's Water Shuriken), it's better to use them conservatively rather than make a wall/hide behind them (Don't even get me started on reflectors/item pull moves). Keeping them consistent for stage control rather than damage (ie throwing out gunmen as barriers, throwing cans high in the air/over and behind them to encourage them to not jump/fall back, etc.) as well as mixing in a fair amount of up-close moves (tilts/normals and grabs particularly as Spirst said) work really well for me.
Funny enough I find in Dog dittos, the more aggressive/less campy one tends to have the edge more often than not.