Although it is embarrassing to admit, I did not know anything about using the thumb to control the line of a baitcast reel in my first six months of using it. As a result, I wasted hundreds of yards of fishing line and became quite the expert at causing a backlash on the line and what anglers like to refer to as birds nests, which are severe cases of backlash. After realizing how to eliminate my problem by thumbing the line, I was able to be free of this agony.
A friend once gave me a unique gift. It was a device with a small electric motor and a special spindle to mount a spool to wind the fishing line. This would have been the perfect tool to practice thumbing with, but I had already mastered the technique. All I had to do was put the end of my line to the spool, flick a switch and all the line from my baitcast reel would be wound on the spool. I had to use my thumb to control the speed rate and flow of line from the reel to the spool, which was not difficult to do. The entire process was completed in a few minutes. The speed was never overrun with precise thumb control of the line. If you have or are able to make such a device, you will surely learn thumbing very quickly.
The same practice can be easily done without the device, but you will need someone to help you. The other person simply winds the line from your baitcast reel onto his or her previously empty reel at a predetermined speed or rate. You get to practice and become proficient at using the thumb for line control which will save a lot of agony and frustration when actually casting and fishing. This may spare you from hearing the chuckles and sensing the eyes of others observing the progress rate of backlash repair, as was my experience when learning how to handle the reel.
The thumb should always maintain contact with the line after the initial release to cast until the setup enters the water and stabilizes. The touch should be very light as if the thumb was a feather stroking the line. Any irregularity will be immediately felt, and the casting can be stopped at any time before a major backlash develops.
I have actually discontinued using the centrifugal brakes on my Abu Garcia 6500 CS Rocket. The brake slots remain empty for many years, the spool of the reel is quite loose, and releasing my thumb leaves no noticeable resistance to the setup when casting. Thumbing has worked like a magic charm for me.
Of course, I would never recommend such tactics to others. My point is simply that with proper practice, definite improvement will surely follow. Enjoy fishing with your baitcast reel. It has to be one of the greatest fishing tools ever created.