一天棒滾 Only a Sky Full of Rod
次後來不見人，只見一天棒滾。八戒在底下喝聲采，也忍不住手腳，厲聲喊道：「等老豬也去耍耍來。」次后来不见人，只见一天棒滚。八戒在底下喝声采，也忍不住手脚，厉声喊道：「等老猪也去耍耍来。」
逐句解 Line by line
After a while the man could no longer be seen — only a whole sky of rolling rod.
Ten characters, and they are the best line in the chapter. 一天 here means a skyful, the whole heaven of it, rather than one day. 棒滾, rod rolling, gives you the sight itself: he is spinning it so fast that the person has gone and only the weapon is left, filling the air. The novel spends two sentences describing the technique and then deletes the man.
Bajie shouted his applause from below, then could not keep his hands and feet still either, and called out loudly, "Let old Pig go and have a turn too."
喝 is hè here, to shout — 喝聲采 is to shout out applause, the noise a crowd makes at a good move, and it is still exactly what you say at a martial display. 忍不住手腳, unable to hold his hands and feet in, is a lovely physical way of saying he could not keep still. He has gone from heckling to joining in within one line.
The disappearing swordsman is an old image and this is one of its purest versions. Two sentences of named technique, and then nothing to see but the weapon.
Bajie's reaction is the human one and the novel gives it straight after. He cheers, then his own limbs start twitching, then he asks to have a go. Watching something done superbly makes you want to try it, which is exactly the impulse the three princes have just had.