yes, indeed, letting them come a little closer, maybe 2/3 ot 1/2 your average weapon's range gives very powerful shots.
In terms of selecting the units, it can be done also by using the grouping feature - not the grouping of the unit cards.
I mean the grouping where its possible to set groups by control+shift+number and recall by control+number. In this way, no time is lostin the selection.