The 20-year-old striker has burst onto the Barclays Premier League scene this season, scoring seven goals, and has even been tipped to win a place in the England World Cup squad under former Baggies boss Roy Hodgson.
He made his first start for nearly a month in the 3-3 draw with West Ham on Saturday and more than justified his inclusion, netting the third goal to earn West Brom a point before being denied a winner by a post.
Downing said: "I'm really pleased. I started here as a youth coach so I know Saido well, I've seen his progression through the age groups and he's a talent, which you've seen against West Ham.
"He's maturing, he's still got a lot to learn, but he's working with good players around him, learning every day. He just has to deal with the success.
"Like anything, you become suddenly a household name and it's difficult for a young boy to get accustomed to that.
"I think he will cope. He's got good people around him. There's me telling him off here and there, keeping him under wraps. He's got to live and learn as he goes along."
Berahino joined Albion soon after moving to the UK from Burundi aged 10 and signed a new three-and-a-half-year contract at the Hawthorns earlier this month.
Following his starring role against the Hammers, Berahino credited his team-mates for helping him learn his trade, in particular Nicolas Anelka, who scored the other two goals at Upton Park.
Downing's biggest decision ahead of Wednesday's clash with Newcastle will be whether to play Anelka following the furore caused by his 'quenelle' goal celebration.
The gesture is controversial in France because of its association with anti-Semitism.
Anelka has stated on Twitter it was nothing more than a dedication to a comedian friend who brought the gesture to prominence but West Brom have conceded it caused offence and he has agreed not to repeat it.
The Football Association is investigating but Anelka is free to play for now.
It was not something Downing expected to have to handle during his spell in charge, and he looked understandably uncomfortable at his press conference on Monday.
The former academy coach took over the hotseat following the departure of Steve Clarke on December 14 and is still looking for his first win.
West Brom have gone nine Premier League games without a victory but they have managed three successive draws against Hull, Tottenham and West Ham.
Downing said: "It's not great sitting here and trying to explain what's gone on at the weekend but from a football point of view I have enjoyed it.
"I've tried exceptionally hard to use the players - 20 players have played in the last three games. We've utilised the squad, I've believed in the squad as Steve did, and they've gone and produced some good performances.
"We're all aware that we want to turn those draws into wins. We've stopped that rot in terms of the four straight defeats but now we're fully aware draws won't be enough."
Downing has already ruled himself out of taking the job on a permanent basis, although the former Cheltenham boss admitted a return to management does appeal.
West Brom conducted interviews last week and Downing hopes Wednesday's match plus the FA Cup meeting with Crystal Palace on Saturday will be his final games in charge.
He said: "The games have come thick and fast and there's no time to talk about it. It's a case of trying to keep the boys fresh and ready to go, preparing for the next game. We've got two quick ones coming round so that's the focus, and it's probably helped.
"(On Sunday) I was told to focus on the game on Wednesday and maybe the one at the weekend. I've always said I'm in a support role here. Has it whetted my appetite? Yes it has, but not (to manage) here."
If Downing decides not to play Anelka then Shane Long should be fit to return after a calf strain. Winger Chris Brunt (back) is also expected to be okay but striker Victor Anichebe (groin) is a major doubt.