Jesus brought life eternal in Heaven for those who want it. That's what needs to be communicated.
If we can understand that, if we want that gift, recognise that we want it, decide to accept that gift - then the rest follows, sooner or later, one way or the other.
(Thanks to the Holy Ghost - the spirit of Jesus Christ - our guide and comforter; all this is available to anybody at any time, for the asking - sooner or later.)
The spiritual war is between those who want what Jesus offers; and those who reject it.
The battles in spiritual war are fought over the undecided souls, the waverers, the drifters, the sleepwalkers, those who Love but whose love is misdirected.
(The undecided souls' personal battles are to understand, to know, to decide, to commit.)
Those who are incapable of love are self-doomed, they are the demons and the servants of demons - they are the other side, but the battles are not 'about' them.
To try and evangelise demons is misplaced effort that might save others. We should be battling them, not arguing with them.
(Of course we may be mistaken that some specific person is demonic in desire. But we must discern, judge and act on that judgment - to the best of our ability. Once one is personally sure - by clear intuition confirmed by the Holy Ghost - then such persons become The Enemy; they are not the subject over-which we struggle.)