You don't want to hand over the vehicle only once second before the buyer has registered the vehicle in his name (or anybody else's but yours)!
When the proper procedures are all followed, such a transaction can be completed within 2 business days, ending with a new matricula issued to the buyer or whom he elects to be put on it.
If you don't follow this advice, you may find yourself trying to hunt down the buyer and his subsequent buyers for years, trying to free yourself from any liability and or face others hunting you down for accidents and other actions involving "your" vehicle.
Don't take advice from ANYBODY suggesting "short cuts" and other local "smart" ideas on how to safe 5 minutes or 100 Pesos.
... J-D.