Practicing your scales in sixes and thirds is essential to playing the accordion. An even better idea is to practice
in time with a metronome
. There are various metronome programs
available for free on line.
For someone who wants a super-metronome that can be programmed to do anything you want, I suggest
the VKO Mundobeat
Whatever program you use, playing in time with a metronome will show you if you really know the scale or not.
To increase your speed, try increasing the speed of the metronome a little each day.
Other metronome programs.Metronome on line
Metronome for PC