Use to shave & pluck over the nose - didn't have an actual UniBrow but there was enough to look very untidy and Neaderthalesque when standing face to face.
I think all the tweezing throughout my teens & 20's finally damaged the folicles and there's almost nothing growing there now.
As for trimming - LOL, I'd probably need a lawnmower. Actually just pinch the eyebrows and pull lightly with my fingers so the loose ones come out - better to get them myself than to have them shed and fall on my face in company.
I also try to keep them at a fairly uniform lenght. I'll run small fine tooth comb through them every 8 weeks or so, and if there's any which have grown to over 1.5 cm in length, I'll trim them individually.