Glasgow ticked the boxes against Munster
Tries by Leonardo Sarto, Lee Jones, Nick Grigg and Scott Cummings gave Glasgow a bonus-point win to lift them above the Irish in PRO14 Conference A.
"Our clean-out was better, we got quicker ball, we defended fantastically and created a lot of turnovers which we used well. But we have a long way to go," Rennie told BBC Scotland after the match.
Glasgow have now won all four of their matches in the competition and sit on 18 points, four ahead of Munster and eight clear of third-placed Cheetahs, who beat Leinster 19-38 on Friday.
"If you'd asked me four weeks ago, you win your first four games, I'd have been stoked," said Rennie.
"We have played some pretty strong sides. We know we can be a lot better than this but I'm happy we made some good shifts.
"We knew it was going to be a real brutal affair and I think we stood up really well in that area. I'm really happy.
"We are trying to play a tempo game and I think Scott Cummings' try was an example of us having a couple of quick line-outs and trying to get Munster out of their comfort zone.
"The key thing is we did what we said we were going to do. We said we were going to be brutal, we said we were going to try to make this place a fortress.
"There was lots of talk about Munster beating us four times last year. We had a game plan that we could play at a pace that made them uncomfortable. I think we ticked a lot of boxes in that regard but we are only four weeks into it."
The Warriors head coach praised the "fantastic" work done by the coaching staff at Scotstoun prior to his arrival and acknowledged the contribution of the noisy support at the sold-out stadium, declaring: "I am loving playing at home."
Glasgow next face Treviso at Scotstoun in a match Rennie approaches with caution.
"I have a lot of respect for Kieran Crowley, who coaches Treviso," he said of his fellow New Zealander.
"There are no easy games in this competition. We'll put a good side on the field next week, and we'll need to,"
Source: @GlasgowWarriors
