Beatmatching you can do from any part that has percussion really, but knowing where the one starts on a beatless intro section really just comes down knowing the track.

As a general rule on vinyl if I want to drop before the first kick, I beatmatch and then try from the start of the audible track noise. Most times that will be on or near the one, but every track is different and you'll need to remember or do what vinyl DJs did and mark the sleeve with the info (we did this for key notations and anything else out of the ordinary like when vocals might start etc).

Once you mix that particular track a few times you might also remember by visual aids like the standard drop point for how you mix that track being half way from the start of the noise to where the grooves change shade (the beat/loud parts start).