I think it was @mack on FGI years back that said he only used a Whippy TempoMaster the first few weeks to warm up for the season , no swinging of regular clubs. This got his tempo and transition very finite and he didn't have the issues of OTT or "hitting" at the ball, etc.
The Ernest Jones/Manuel de la Torre handkerchief and a pocket knife or tennis ball on a string is the same idea.
Whippy TempoMaster is great I still have two (driver and 5i) and you can hit balls but Orange Whip is great also.
Here's Doc. Orange Whip can be used same way, @Beatfarmer/Rory on FGI pushed them for awhile.