Using Rekordbox, the analyzed music will show you the very exact BPM of each track. Setting the pitch fader is usually done the moment the track is loaded in the player. It takes only a second and there’s no need to check if the speed is the same unless you play tracks with variable speed like old disco tracks. I use the 6% setting on the pitch fader and adjust the pitch by raising it to the exact same frame/BPM on both tracks. Like 124.2. Each decimal has 5 frames, so it’s important to set each track the same.
Done that, I can start the track a minute before the transition is supposed to happen, take off my headphones, and still know that I will be in perfect sync during the whole transition. This is the ”new” way to do it and it’s possible because the new club gear is so exact. Most of us older dudes that started with vinyl still does it the ”old” way Terry_42 describes it. That’s because when playing vinyl, the speed shifts slightly over time, so during long transitions, you have to adjust the speed or nudge the platter during the transition. It works, but you can hear the DJ nudging the platter as the tracks goes out of sync for a ms each time.
Playing soul/funk/disco originals, this is still the way I play, even on the latest club gear, and for some people it’s actually the way they want to see the DJ play. It makes you work the platters through the whole mix, versus playing new house music where you can focus on using the mixer/effects instead, or stand there waiting until it’s time to change tracks… doing the hearts and throwing cakes or whatever is your way out of boredom 🙂 . Some DJ’s just speed up their mixing giving people 30 sec’s/track to avoid the waiting… Whatever fits you and your crowd 🙂 .