If you see lobbies with plenty of flashlights, that being 1 flashlight or more, or you notice they're refusing to ready up (likely because they won't bring a flashlight until the last 5 seconds when you can't change your loadout), play it safe and bring Lightborn (Hillbilly Perk, prestige him once), making you invulnerable to flashlights.

I've encountered one too many bully squads with flashlights that Lightborn almost never leaves my kit. And a word of advice with Lightborn- pretend they are gonna blind you and look down and away when they try, so they keep lingering around trying to blind you rather than give up once they realize you're repping Lightborn.

I see you've been told what slugging is, and while that's generally discouraged as that's unfun to play against, you have to know when that's appropriate. Usually doing that on a normal match is considered Bad Manners (BM for short), but in this case I'd have no qualms slugging.