The lines which control the speed of the blink are the two delay(1000); lines. To make the LED blink twice as fast, change these to delay(500);. Change these values to different numbers and see the results!
Making the INCREASING and DECREASING values bigger will make the LEDs increase or decrease faster. You can make them different numbers so that the LEDs increase faster than they decrease, or vice versa.
There are two ways to complete this: in software and in hardware.
In software: brightness = analogRead(KNOB1)/4; to brightness = 255 - analogRead(KNOB1)/4; and chaseSpeed = 200 - analogRead(KNOB2) / 6; to chaseSpeed = analogRead(KNOB2) / 6 - 200;
In hardware: You can also reverse the direction by swapping the red and black wires on both sides of each potentiometer.