[Imp]

Covering both your posts here only need the one really
Firstly have you read the guide probably covers the basics (can't remember)
The faster you move the less accurate your fire & the easier you are to detect.
Accuracy goes up if you maintain target lock on the same unit the 3rd shot has them zeroed in.
Because of this change units if fired on or the next shot at it will be more accurate.
Fire with units in cover or furthest away first as most likely to survive unscathed.
Dug in units are hard to spot & very hard to kill best infantry vs at any range are snipers & MGs, for any real chance though you need a strategy to get you within 150m preferably adjacent & shoot at point blank.
Thats what your smoke is for do not move into it place it as a screen to reduce the number of enemy that can fire on you or move up without being shot at.
Getting in a slugfest with dug in units is suicide you need to greatly outnumber them fire some people preferably from stationary then move others closer for the kill.
So use your smoke to help you concentrate your force on a few units by screening the rest out of the fight dig them out & move on, that being said you will need practice they are far tougher than infantry in the open.
The other use for smoke is suddenly finding you are outnumbered if taking a shot means 5 units are going to fire back at you not shooting or placing smoke might make more sense.
Infantry smoke does not last long less if visibilty is high but generally nearly gone by the next turn, other types last longer.
Your first half a dozen games would not worry about the outcome just try & come to grips with basic strategies & see what works & what doesnt.