Using a pizza cutter will make the job easier and neater.
Your focaccia will keep in an airtight container for a few days. To revive it, just put it under a medium-high grill or in a halogen oven at 200°C for 2-3 mins.
Metric kitchen scales are an inexpensive yet invaluable gadget to enable accurate measurement of ingredients. Store them upright in a cupboard or over your worktop and they'll only take up a tiny bit of space. Click
HERE for the ones I use (UK Link). For U.S. option click
HERE.