The Cards boss said in the build-up that Watford would “thrash” his team but they gave a great account of themselves.
The Premier League side did win 2-0 but the National League South club weren’t out played.
"I’m so proud of the team, the fans and the volunteers,” Dowson said.
“We gave it a real go. We needed to have confidence in ourselves but it was always going to be a big ask.
"I am very proud of the players. We have had a good start to the season and we are still up there in the league and fighting.
"Watford were great. Their manager was great and the way their players acted was fantastic, so we're really thankful for that."
Hornet boss Javi Gracia said: "We are happy with the performance and the result. We came expecting a lot of this team.
"We played with the same respect until the end. I like the attitude of my players. They showed they are available for the next games.”