The Finn has not raced in GP2 or Formula Renault 3.5, so has little experience of making in-race pitstops ahead of his grand prix debut in Australia next month.
But with Williams always planning to conduct extensive pit-stop practices today after sending its full race team to the final day of the test and still able to work on that despite the bad weather, Bottas has been able to improve that aspect of his game.
"We did plenty of pitstop practices, so even though the weather was like this, we did some good," he said when asked by AUTOSPORT what he was able to gain from his running.
"I improved a lot during the day, that was really valuable.
"The positioning, the pulling away and also coming into the pit-lane and braking late for the line is all new to me so I'm learning more and more."
Bottas is satisfied with the progress that the Williams team has made with the new FW35 during the four days of running at Barcelona.
After being impressed with the car on his first taste of it on Wednesday he believes that there is still more to come.
"We are on the plan," said Bottas. "We missed some laps because of the rain but it was the same for everyone.
"There are some balance things in the car that we can still improve, especially with a little less fuel but we are aware of the problems that we have and they are all fixable.
"We understand it more and more all the time.
"Straight out of the box, the car was very good. Now, it's even better and we can get it in even better shape for the next test."
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