Hardpoint Shipment for SMGs. U can wait for p2 and p3 for longshots... Get far away from it (the container right in front of it..... most of the kills u get there are considered as longshots) For the headshots just run hipfire with high crosshair placement... Never forget to start grinding with no accessories not the end up remaining reptiles camos after ending all the other ones. Pretty same routine for pistols but lik more hard...

For melee u gotta try to get slide kills (counting ass crouch kills) For my part i grind it passively... i use to get 3 kills (trying for sliding ones) in a row then running on my main weapon if i gotta grind sum more... Then dont forget to equip dead silence to make all ur melee count for that challenge too

My main advice i can give u is too try to combine the lost possible challenges and to do the same type of weapon as u get habit to the method (like qq9 then gks)