There’s probably tutes on acapellas out there somewhere. I would use audio software to do this ahead of time.
For a super-accurate method, I’d line up the Acapella with the original track. Add extra silence if needed to make sure the two tracks are identical lenghts, then export the prefectly matched acapella (PMA) Import the PMA to your dj software, cut and paste the BPM from the original track, set your cue points and go.
If you’re just layering an accapella to drop out the chorus, you can just approximate. Acapellas don’t have a hard start, so its impossible to trainwreck with them.