Noun
palmful (plural palmfuls or palmsful)
Enough to fill the palm of one's hand.
I shampoo my scalp with diluted shampoo (ratio of about 1:10 shampoo to water) and rinse really well, then add half a palmful of GTN, brush through, and that's it! Source: Internet
She poured a palmful of shampoo and stood very close to Pyosz's back to rub her head. Source: Internet