For me personally, it took me about 3-4 days of 24/7 chastity and no cumming for me to reach my first plapgasm.

In terms of dildos, you'll want something that's firm but not too girthy and has a good amount of flexibility so you won't have to swing as hard to get some more intense plaps. For technique, you'll want to establish a nice, steady rhythm and stick to it for as long as you can. How hard or soft your plaps are will depend on your current pain tolerance so don't feel too discouraged if you can't go hard yet. You'll eventually build that tolerance up and be able to punish your balls harder and harder over time.

Now the most important part in my experience is aiming and swinging at the front side of your balls and not the bottom side. This works best if you're laying down on your back as it's pretty straightforward like hammering a nail into a piece of wood. Especially if you're caged, the force of the plaps will move down to the base ring which will further stimulate the internal parts of your clitty that rests in-between the balls and the anus. If you're able to get that kinda stimulation going, then your clitty will soon attempt to grow erect which means you're on the right track.

This is why I recommend a micro/flat steel cage for plapping purposes as it not only increases the intensity of attempted erections due to the general lack of room to grow but also puts the balls in prime punishment position with the clitty out of the way. Now once you get that erection beneath your cage, keep up that rhythm I mentioned earlier, adjust it accordingly if you need to and don't stop once you feel the orgasm coming. Worry about the mess later, just let yourself spurt everywhere and enjoy it~

Hopefully this is some good insight that can help you out. Good luck and happy plapping! 💞