All I can really recommend to improve sniping would be, if you wanna take the csgo route and have that carry over, warmup routines of many pro players/esea players that I can show you but I don't know how much it'll help. As for tf2, a balance between sniper on community servers, mainly badwater and upward, where usually the players are better or know what they're doing better than most pubs and mge scout. Usually, invite-level scout players are as good or better than top highlander snipers.
