演演方法 He Tries the Method
這大聖不管他死活，捽脫手，拽大步，徑出了芭蕉洞。正是：無心貪美色，得意笑顏回。將身一縱，踏祥雲，跳上高山，將扇子吐出來，演演方法。將左手大指頭捻著那柄上第七縷紅絲，念了一聲「𠲛噓啊吸嘻吹呼」，果然長了有一丈二尺長短。这大圣不管他死活，捽脱手，拽大步，径出了芭蕉洞。正是：无心贪美色，得意笑颜回。将身一纵，踏祥云，跳上高山，将扇子吐出来，演演方法。将左手大指头捻着那柄上第七缕红丝，念了一声「𠲛嘘啊吸嘻吹呼」，果然长了有一丈二尺长短。
逐句解 Line by line
The Great Sage, caring nothing whether she lived or died, shook off her hand, strode out with a great step, and went straight from the Banana-Leaf Cave.
拽 is zhuài, to stride or haul, not zhuāi. 不管他死活 — caring nothing whether she lived or died — is as cold as the novel ever gets about a character it has just spent two passages humiliating.
Truly it was a case of: with no heart for beauty he coveted none, and getting his will he turned back laughing.
This couplet is introduced by 正是 and yet it is not verse. 維基文庫 leaves it unindented, which is the printer's own test and the one the project follows: narrator-inserted set-pieces are set off on the page, and this is not. Of the chapter's six instances of 正是, only one — in the final block — actually announces a poem. 得意 takes dé. There is a pun in the last three characters worth catching: 笑顏回 reads as "returns with a laughing face," but the last two characters also spell the name of Yan Hui, Confucius's favourite disciple, whose byword was cheerfulness in poverty.
He gave his body a spring, trod the auspicious cloud, leapt up onto a high mountain, spat out the fan and tried the method over.
Both instances of 將 are jiāng, fronting the object. 演演 doubles the verb: he is rehearsing, not performing.
He pinched the seventh strand of red silk on the handle with the thumb of his left hand, said once the words huí xū a xī xī chuī hū -- and sure enough it grew to a zhàng and two chǐ in length.
長 divides again — 長了 is the verb zhǎng, to grow, and 長短 the noun cháng, length. 捻著 takes the continuous zhe. The rare character opening the incantation, 𠲛, makes its second and last appearance in the chapter here; the source encloses the formula in one style of quotation mark this time and another the first time round.
The exit is three verbs long and entirely without ceremony. He shakes off her hand, takes a stride, and is gone. The novel has just shown him humiliating a woman he spent an evening deceiving, and it gives him no backward glance and us no moment to dwell on it.
The couplet that follows is the storyteller's verdict rather than the narrator's, and it is offered as praise. He had no heart for beauty, so he coveted none; he got what he came for, so he laughs on the way home. Whether the first half is true is a question the previous two passages have left us very well placed to consider.
What he does on the peak is a rehearsal. 演演方法 — he tries the method over — and the fan behaves exactly as instructed: seventh strand, left thumb, seven syllables, one zhàng and two chǐ. The system works, and the working of it is what makes the discovery of the next passage possible.