The contaminated towels need to be discarded in biohazard waste. Organization in setting up and in doing this exercise is necessary to get good results. Read the entire exercise. Working in pairs helps. Decide who does what, especially when transferring bacteria and diluted phage to the top agar tubes.
Reasonable speed is necessary to avoid over-heating the samples.
Time is also of the essence when pouring the top agar onto a petri plate to facilitate a smooth and even layer. On the plates, also label with date and initials for later identification. Aseptically mount a pipet tip on the P-100 pipettor, as demonstrated, by pushing the pipettor tip into the top of the disposable tip in the box and lifting it free of the box without touching any surface with the tip. Blow out tip into tube 1, then mix by carefully aspirating up and down three times with the pipet. Discard tip and mount a new pipet tip.