とばかりに says someone acts as if the action were saying something: "as if to say". What they seem to say goes in front, usually as a quote in 「」, and the action comes after. Nobody speaks; the words are the speaker's reading of a gesture, a look or an attitude.
きごう「きごう」。
He dashed out as if to say "I've been waiting for this!"
きごう「きごう」。
She turned her back as if to say "I don't care anymore."
きごう「きごう」。
The boss pointed at the clock as if to say "Hurry up."
The quote can drop its 「」 and become a plain clause describing the attitude. Since the pattern reads someone from the outside, the one acting is someone other than the speaker.
、。
He stayed silent, as though it had nothing to do with him.
ここぞとばかりに
is a fixed phrase: someone jumps at a chance they have been waiting for, "seizing the moment".
。
He seized the moment to push his own opinion.
、。
When the sale started, the customers seized the chance to stock up.
とばかりに or ばかりに
without と is a different pattern: "just because", a cause that led to something bad. It follows a plain-form verb, with no quote in front.
、。
Just because I said one word too many, I made her angry.
きごう「きごう」。
My mother sighed as if to say "I told you so."
means the same as とばかりに with the "saying" spelled out: the gesture is so plain the words might as well have been spoken.
とばかりに belongs to written narrative: novels, essays, sports reports. In conversation you would say .
きごう「きごう」。
The teacher looked at the clock as if he wanted to say "Hurry up."
Lingaku