I'm branching into scout and it seems like enemy scouts are really annoying to hit. The beanpoles have a small hitbox so the shotgun doesn't do much damage unless it's point-blank, in which they can just blast me in the face. On the other hand, I have a slighly better aim than most pub scouts, but mostly due to my strafe-shooting technique and prediction rather than actual reflex. Does anyone here main scout and have any advice on mentality? Being a pyro main, I often can't resist sneaking up to people, which seems to be even easier as a scout except you can't set people on fire.
Honestly, I main scout (whenever I can find a server not choked with minsentries, grrr) and quickly aiming the scattergun is still tricky for me. It comes with practice. Its high damage and high capacity enough you can get by without having perfect aim. Once you do have good aim, your scattergun will easily outdamage the flamethrower against single targets. If you find yourself sneaking up on people a lot the force-o-nature or the backscatter might be an effective choice but the scattergun is still the undisputed king of scout weapons.
The most important thing is getting your movement down. Learn how to double jump unpredictably to dodge rockets and grenades. Generally this means jumping one way and then double jumping the other, but you can also do stuff like jump over your opponent or jump close to shoot and then jump back for distance. Once you expend your double jump, your trajectory is almost completely predictable and you're vulnerable, so wait as long as you can afford to (and ideally bring the atomizer so you get a third jump). The scout is kind of a stealth class, but instead of being hard to see you're hard to predict. There are a lot paths you can go down as scout that would require self-damage via rocket jumping if you were a soldier. Learn to do stuff like jump on roofs, over gaps, or up cliffs. Learn it well enough that you can do it in the middle of combat without thinking about it. Once you learn how to leverage your speed you'll be a terrifying force of nature constantly appearing behind the enemy to shoot them in the back. As a side note to this, try to play modes like payload, king of the hill and control point where mobility is useful and the maps are open. In modes like capture the flag and attack/defense scout is more of a gimmick than a necessary part of the team.
Like spy, you want to limit how long you're in sight of enemies. Get in, do your damage, and get out as quickly as possible even if that means giving up a kill (if it feels suicidal you're probably going to die before you make the kill anyway). The go-to way to fight heavies is to run around a corner, meat shot them, and then leave before they spin up. You can go toe-to-toe with a soldier or another scout skill being equal (even a pyro if you're good at controlling your distance from the target), but you shouldn't stick around for a fight where there are more enemy fighter classes than friendly ones. Unless something important is at stake like an objective or your own medic dying. If you see a sentry, announce it to your team with the voice commands and then leave. You can bypass them with Bonk! but this is usually a waste of time and from a tryhard perspective its hard to justify Bonk! over any of the pistols except maybe the winger.
Most important thing: never stop moving. If you're sitting in place to ambush an enemy, you shouldn't be playing scout.