The Belgium international was introduced for the final quarter of the game and caused constant problems before adding to Matthew Lowton's first-half opener. It enabled Villa to end their run of 14 Barclays Premier League games without a win as they registered only their second victory in front of their home fans in 10 months.
Lambert, who celebrated his first league win as Villa boss, said: "I thought Christian was unplayable. He was an absolute threat. The great thing is he's only 21, only a kid and still learning."
He added: "He has a really good game for the national team against Croatia in mid-week and, if you're holding your own in that company, you're doing alright.
"Everything is a culture shock for him at the minute but he was excellent. The goal will give him confidence. The crowd will go with him. You heard the crowd's reaction when he came on."
Lambert was delighted with Villa's overall performance as they built on the creditable 1-1 draw at Newcastle before the international break.
He said: "I thought they were excellent, right from the off. We thoroughly deserved it, against a really good side which has been flying. I thought we were well-worthy of it. The tempo and the way we played was excellent. I have nothing but praise for the lads."
Swansea defender Ashley Williams was at fault with Benteke's goal which completed a nightmare week for the skipper after being part of the Wales team beaten 6-1 by Serbia.
Swans boss Michael Laudrup said: "Ashley is a super guy but he has had a very severe week. When you lose a club game, you always have the next one to recover. But when it is an international, at the start of a World Cup campaign, and you lose two games and one result is very savage, it hurts.
"Then four or days later you have to play a tough away game. I think he did well. Of course, it was a mistake at the end but, whether it was one-nil or two-nil, doesn't make a big difference. I said to him afterwards to now go and relax and I am sure knowing him he will come back after a couple of days with his family and have a huge game against Everton."
Source: PA
Source: PA