The reason to use organza for tambour rather than tulle is that organza doesn’t stretch at all no matter which direction it is pulled. Tulle stretches a lot in one direction. That means that as you embellish on tulle the fabric stretches and when you remove it from the frame, your work will pucker. Also, as you were working your fabric was stretching, which was causing you trouble with dropping the thread from the hook. Another reason for avoiding tulle.
I love learning about all the techniques! I might never use them, but knowing about them feels enriching, because I love textile handwork so much. 😍♥️♥️😍
I bought probably about 20 or so colors/shapes of sequins and I knew I wanted my petals to skew lighter rather than darker so I started out by just doing little blobs of colors together to see how the looked about 10 feet away. Then I narrowed down to my favorite sequin combination and when I place the sequins on it's completely random but the ratio of sequins I predetermine when I am stringing sequins.