To do an abubaca, you must first know how to hop and role backwards. Approach the object with moderate or slow speed depending on your comfort level. Hop as needed and brake as soon as you get your rear wheel off the ground. it helps to use only one finger, either your middle finger or index finger depending on where your brake lever is. Land the rear wheel on the ledge or whatever with your back wheel and get your butt behind the seat as if doing a manual. This will keep the front end up and keep the weight on the back wheel. Stall for just a second and keep your balance for as long as you can. When your ready to dismount, hop backwards by pulling all your weight back and pumping. Try not to hit your front wheel on the ledge. When you land, don't forget to back pedal. You can role back as long as you want. When your done tap the back brake and pivot in the direction you want to spin, pulling out and riding away smoothly.