If you push the tube too far, the end of the tube may go back up inside the oil pan. When you start hearing the bubbling noise, pull the tube out slowly until the bubbling noise stops (the end of the tube is back into the oil bath again). When you hear the bubbling noise again the second time, push the tube in and out slightly to get a feel of the oil level in side the oil pan (by hearing the bubbling noise). After some practice, you should be able to insert the tube to the bottom of the oil pan without overshooting. When you have 3 to 4 qt. of oil out, empty the storage can and start all over again.
To clean the tube for storage, hang the tube at mid point and do not disconnect it from the storage can yet. Remove the pump and put the open end of the tube into the opening where the pump was. The purpose of doing it is to drain all the remaining oil inside the tube into the can (it takes a while).