Johnson said afterwards: "It was a good team effort and we deserved to win.
"It is a massive lift for us, it's how you handle that situation. We have to kick on now.
"We play Dundee United next week then teams in the bottom six in the next four games after that so we have to make sure we start to pick up points."
Johnston was full of praise for his striker Boyd, adding: "He's been playing like that recently, you can see he is working a lot harder.
A lot of people criticise his work-rate but he's desperate for the team to do well, he's a real inspiration to the younger players.
"It was an unbelievable finish - that's what he is capable of. He was unlucky not to score a couple of other goals as well, he's top class."