Hamilton said he had "absolutely no problems" as he led team-mate Jenson Button in a McLaren one-two in the morning, and was then fastest again before rain hit the afternoon session.
"It's been a really positive day. I'm very, very happy," said Hamilton. "We made some good changes to the car to get it dialled in, and we're on the right path, but we've still got some work to do. The Red Bull looks very quick, so does the Lotus, and obviously the Ferrari as well. So we're by no means feeling comfortable."
He expects several rivals to show much stronger form in Saturday's qualifying session than they did in practice: "I feel good in the car but practice is completely different to qualifying.
"Tomorrow when we get into qualifying I have no doubts that Fernando [Alonso] will all of a sudden find half a second and the Red Bulls will have of a sudden find a chunk of time. I think we're not in a bad position."
Hamilton has only scored four points in the three races since his Canadian Grand Prix win, but feels he is in excellent form going into this weekend's Hungarian race.
"I'm on it and I'm happy to be on it," he said. "I feel like I've been on it all year, but I feel a lot of support from the fans, the car feels great - as it did in the last race - and it's all in one piece at the moment. I'm just focusing on trying to maximise every lap and every opportunity I get out there."
