Do this workout to master strums. Here is the “scuff” approach I use with students to REALLY nail down and clear up rhythm issues. This one is for 3/4 time - like a waltz, or lazy country tune. This example is taken from the rhythm in the song “More Gun”. https://vimeo.com/1141667370/077c45fbc0

So, Andrew has me workling on an old Carolan tune, Planxty Irwin, in the key of D and using drop D tunning (on the 6th string). Initially, I had my doubts about whether it is worth it to learn the somewhat different chord fingering, but I'm going along. Now that I am working on the tune, I notice that having both the 6th and 4th strings tuned to D makes a very nice drone that works well with an Irish tune!