If you drain a ball, it starts you over at the prior lock level.
Couch - holds 3 balls (3rd must be last ball)
TV lock - holds 1 ball (must be last ball)
Garage VUK - holds 1 ball (must be last ball)
Otto loop - holds 2 balls (2nd must be last ball)
Itchy & Scratchy - holds 1 ball
So... for when you have to lock 5 balls... lock 1st in I&S. Lock 2nd in Otto. Lock 3nd and 4rd in couch. Then your 5th will most likely be locked in the garage VUK or the Otto loop, unless it's already on the upper playfield in which case you can also use the couch or the TV.