Townsend has been Scotland coach since May 2017, after five years in charge of Glasgow Warriors.
He has won four of his six games in charge, including a record 53-24 win over Australia in the autumn.
Barclay praised Townsend's fresh approach to training, calling it "intense and stressful".
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"Some of the Glasgow guys were more used to it and used to that dynamic with changing scenarios, always asking questions," said Barclay, who plays club rugby for the Pro14 Welsh side Scarlets.
"It is never mundane, it is never the same thing, which I love," he said at a Six Nations launch event in London.
This is reflected in Scotland's playing style under Townsend, described by Barclay as "organised chaos" and epitomized by Scotland running world champions New Zealand close in last year's autumn internationals.
The All Blacks won 22-17 in a thriller at Murrayfield, with Scotland pushing for a winning try into the final moments of the game.
Scotland face Wales in their opening Six Nations fixture on Feb. 3 and Townsend has been getting tips from Manchester City coach Pep Guardiola in advance of the tournament.
"The biggest thing from meeting Pep was seeing a coach be so passionate about the details and about how to bring the best out of the players. He was so excited about it," said Townsend, who gave Guardiola a signed Scotland jersey.
Scotland's form under Townsend sees them come into the Six Nations as outside contenders, capable of upsetting any team with their frenetic attacking play.
Barclay said the plaudits coming Scotland's way have been flattering but warned of the threats posed by the other teams in a tough Six Nations schedule.
"I have said a number of times today that Ireland and England didn’t lose in the autumn. England have lost once in two years. Plus, Wales have done well in the Six Nations, French clubs have done well in the Champions Cup," said Barclay.
"So that is the challenge and I am not naive enough to think we are going to win just because we are going well."
Townsend said he couldn't remember a time when northern hemisphere rugby was so strong, off the back of impressive autumn results.
Scotland haven't won the Six Nations since the expansion in 2000. However, Townsend was a player when Scotland won the final Five Nations tournament in 1999.
Winning as coach though would be more special.
"Six is better than five," joked Townsend.
"It is a better feeling than when you are a player, seeing the boys go out and defeat Australia. Winning the Six Nations would be huge for all of Scottish rugby."
(Reporting by Jack Tarrant; Editing by Jon Boyle)
