Ok there are some things that should have been in the manual in more detail...
Ok where you start out... select 1 soldier and "X" for examine to look into the nearby weapon crates. In one should be AT mines and the other should be AP mines. I would force the soldier to put ALL his belongings into the weapon chest (select ">>>") then double click on the mines (which will add as many as you can carry to your soldiers' inventory).
Now you have some mines...
Tell the soldier to go to a spot and select the "mine area" icon and then you will see a little red flag where he is supposed to put one...
I notice you can somehow do a line but I just hold SHIFT and select numerous spots for as many mines as he has.
Once you have mastered that...
Now get 3 soldiers doing mines at once...
About swapping out stuff... if you have a soldier that needs to resupply some cannon... again.. make him empty his inventory into a crate (so he has max room)... then open a crate / truck etc with "X" then select the shells (example) and put them in the soldiers inventory..
Next, go to the empty cannon and hit "X" (examine) on the cannon with your soldier... and then transfer all the shells to the cannon. Repeat as needed.
Could be easier but isn't too hard once you see how they designed it to work.
For that mission you also may want to transfer extra shells to your cannons... it is too hard to resupply them mid battle.
About direct fire over AI fire... sometimes using direct fire... you can focus where and what you want to and even get rare shots out of the normal weapon range... plus it is just fun mowing down infantry with big guns manually.
Hope this helps!
