Another option that i use alot when i am cross genres is cut out your highs and your lows of the 2nd track…the highs and lows are often where the rhythem of the song is found while the mids is more of the synths and vocals, to blend in your 2nd track…this doesnt always work but for the occasional song it does.
Another option that has worked for me, but is a little trickier…sync the 2nd song to the first song with keylock, have your 2nd song be the master tempo, drop the 2nd track in on the beginning of the build, and on the outtro of the 1st song…when the 2nd song is about to drop kick the bpm to the original tempo of the 2nd song and off you go.