Anderton
I cheat 
I lay down quarter notes in the piano roll view. Then copy those and copy them again, offset by an eighth note. Then I copy that pattern and copy it again, offset by a 16th note. Then the same thing, offset by a 32nd note. Then a drag a line across all the velocity tails so the velocity increases over the length of the measures.
Nice! I would do one beat at a time and then copy, but I like this method of doing a measure at once.