Loop roll.
Track A is on outro, as u mix in track 2 during the build, 16 beats before the drop use a 1 beat roll, then when its 8 beats before drop do a 1/2 beat roll, then slowly put a HP filter on the loop roll, cut as the drop to the 2nd track hits.
Loop Roll Gate effects
Same thing as above yet apply a gate to the build of the 2nd track, apply the same loop roll while applying the gate to the 2nd track and off you go.
I use traktor where i can have multiple effects going and apply to different decks so i dunno what u are using.
The new Traktor 2.6 has some freaking AMAZING macro effects that im still fully getting used to before i use them on my next gig.