I sometimes use the word "spot check" at work. When we write a report and have a lot of tables in it, we want to make sure that numbers are all correct. I ask someone to take a look and see if everything looks correct. I may ask someone to do a spot-check, which means that I am not expecting my colleague to check everything.
仕事でレポートを書いたら表の数値などが正しいかなどを完璧にしますが、スポットチェックと言って、同僚に一部で良いので、数値をチェックしてもらうことがあります。
I helped You (his name) with his pronunciation earlier today. I realize I did do a through check while I was helping him (so it was not exactly a spot check). I was helping him to keep a poker face with any sounds, consonants or vowels. Especially he needs to be careful with some vowels like U and O. Japanese people tend to use rounded lips for these two and when they do they sound very Japanese (it's subtle).
ゆうさんにスポット指導をしてみました。スポットと言っても良く考えると、ちゃんとやりましたけどね。気を付けるのは、特にウとかオのときに唇が丸まらないようにすること。そうすると、喉のほうも力みがきて、母音が日本語っぽくなります。
The trick is to smile and produce these sounds while half-laughing. When you laugh, the throat/neck will relax and with that you will be able to articulate sounds well.
笑いながら、笑う時の声で言うと、リラックスしていい音が出ますよ。