Early tip for soldiers: Slushie Bombs.

[Anker]

They're renewable, they're cheap, and you can farm the materials in Flathills for at least, oh, 15 per reset. Tossing these art a soldier will stunlock them for a good 5 seconds, which is enough to run in with your melee and start jabbing them in the face. Protip- Don't be standing too close when it lands, or else you'll be frozen, too.

[Anker]

Also holds them still to line up a scrapshot headshot, pistol or shotgun. Though you could try your luck putting up a barricade and hoping they're not competent enough for a headshot- Trading for concrete bags is super cheap. (Albeit, super specialized)