信手 (xìnshǒu, 'trusting the hand') is a literary adverb — you'll see it before verbs like
翻 (fān, flip),
画 (huà, draw),
写 (xiě, write),
拈来 (niānlái, pluck out). Compare the set phrase
信手拈来 (xìnshǒu niānlái), 'to grab effortlessly' — said of writers/artists who can produce quality work on demand.
