Kamara joined last month on loan from Major League Soccer club Sporting Kansas City and his introduction just before the hour breathed new life into the Canaries, who were trailing to a first-half goal from Leon Osman.
The 28-year-old powered in a header from a corner to equalise with just six minutes left - but there was still time for Norwich to grab a first win in 10 Barclays Premier League games as Holt scored at the far post deep into stoppage time.
"Kei is a different type of player to whom we have up front and we are delighted for him," said Hughton, who had started with Holt and January signing Luciano Becchio in attack.
"He had been here to England before (on trial at Stoke) but these things are all about timings and it was right for us.
"He has that ability to get beyond and is good in the air, he gives us good possibilities.
"It is always a bit of a risk because you are bringing players over who you don't know how they will settle into the league, but he is a lad who wants to do really well and it is a good opportunity for him."
Norwich's hard-fought victory gives them some more breathing space over the battle for survival, having finally won in the Premier League for the first time since December 19.
"Once you are 1-0 down and you get back to 1-1, you have to be honest and say you settle for that," said Hughton, whose side had gone on a superb 10-match unbeaten run earlier in the campaign before hitting the buffers over Christmas.
"But the lads wanted something different and showed great drive and determination to get the winner. We are past the 30-point mark now, so for us and the team, that is a big confidence booster."