The winger moved from Croatian side Osijek just before transfer deadline in a £2 million move to the Ibrox side.
Grezda is in the Albanian squad for next week’s Nations League showdown with the Scots at Hampden.
But Albania coach, current Under 21s manager and 67-times capped former striker Bushi admits he was surprised he agreed to move to Scotland.
He said: “When you look at just how talented Grezda is, we all expected him to move to a bigger stage than at Rangers.
“He’s a player who can be world class.
“But I am sure he will be able to quickly prove himself at Rangers and knowing his qualities, he will make a big impact.
“He deserves a big transfer and I think he will do well in Scotland.
“He is a very important player for Albania and when he plays well, we tend to do well. Eros has worked very hard and I wish him luck.”