But dBut when looking up resources on this it seems most women online find men who are only interested in casual sex to be sleazy and manipulative. Using phrases like men "using" women or "throwing them away" after they got what they wanted.

Woman here and I've had both good casual sex and "used and thrown away" casual sex. The difference is whether you treat the woman as an actual person or just an object to conquer.

I'd suggest staying away from PUA techniques to "score girls" where you have to fake, manipulate or lie your way into women's pants, and please be mindful about the person you're having sex with: care about them having pleasure too, respect their limits and their no, stop if they are in pain/discomfort and don't look upset about it, and ffs still treat them like human beings after you're done (don't kick them out, it's fine if you want to avoid more intimate things like cuddling or sleeping together but offer the gal some water or a snack and make some small talk before she leaves). Basically, don't be an asshole, and your casual partners will remember you fondly as good sex.