the slowness of the LED to turn on has three components:
1) longPressDelay: make sure that youre not trying to do a single-press {this is set to 400ms}
2) check the conditions to find the correct action {this can take like 500ms, but i with the current setup its much less}
3) initialize the camera {camera app wouldnt work if i kept the camera loaded up all the time} {this takes maybe 1000ms}

for me, the LED turns on in ~2s. you can make it faster by removing the condition for all longPressActions {this would make it work even when the phone isnt locked, tho}, and decreasing the longPressDelay{this would make it hard to do single click actions}. its never going to be less than a full second though