If you can do cross on bottom bld, then you should have no issue doing the cross while looking ahead to see your first pair. I'm not going to lie, sometimes when I'm doing my cross (I still do it on top, but find an R2 or L2 etc that I turn into an r2 or l2 to get the cross on bottom), if I see a pair that's already paired up that will get affected by my next cross move, I'll do a quick RUR' or something to get the pair out of the way so I have an easy insertion, then finish my R or R2 etc for the cross.
One way to see how to do cross on bottom is to plan out your cross on top, don't execute it. Take your cube and rotate it, x2 or z2 it doesn't really matter, now look at how you did your top solve planning and then take those moves and turn them into what it will be with cross on bottom. What you have to do with this though is make sure you understand how the pieces move as you probably won't be able to plan for top then "translate" the algorithm into one you'll use for x2/z2 in 15 seconds (actually 12 but you know). I'm only suggesting this technique so you can see how pieces move around while doing cross on D.