Ad → landing page → 3-field form → WhatsApp opens with the lead's details pre-filled. That's it.
The reason it works: no email lag, no dashboard to check, no missed leads sitting in a spam folder. You reply from your phone, in your pocket, in your normal chat app.
Speed to first reply is the single biggest factor in whether a paid lead converts. WhatsApp-first flows win because they cut that delay to almost zero.