Why were the granaries full of grain?
Malbim: This was via Hashem's Brachah, above nature.
What is "v'Heshiku"?
Rashi: It is an expression of making noise, when [grape juice] flows from the winepress to the pit.
Radak: This is like v'Hetzifu - "Asher Hetzif Es Mei Yam Suf Al Pneihem" (Devarim 11:4). I.e. the winepresses were full to the point that the wine or oil floated on them. Chachamim said, if Mei Chag (water for Nisuch ha'Mayim) became Tamei, if Heshiku (they inserted them in a Mikveh until water of the Mikveh floated over them) and afterwards were Makdish it, it is Tahor. If one was Makdish them and then did Hashakah, it is Tamei (Pesachim 34b. This is because Hashakah does not help for Hekdesh.)
