Someone (mang-) flattens something (-en).
pilpil
Mangpidpid ka so inapoy tan arwaro mahap na.
Flatten the cooked rice so (the bowl) can take more.
Pidpiden mo tana tan maypatwa.
Flatten the soil so it will become hard.
pipidpid
Someone (maka-) puts hairdressing oil on his/her hair and smooths it down.