slick as whistle (adverb) readily: quickly; effortlessly
Sinonime: at once, at the drop of a hat, cheerfully,
eagerly,
easily, facilely,
freely, gladly, hands down,
immediately, in a jiffy, in no time,
lightly, no sweat, nothing to it, piece of cake,
promptly, quick as a wink, right away, slick as whistle,
smoothly, speedily, straight away, swimmingly, unhesitatingly,
well,
willingly, without delay, without demur, without difficulty, without hesitation
Antonime: unwillingly