I use plain old "egg" yarn in different colors treated in advance with Water Shed as both a sighter and a strike indicator.
I don't bother to make up yarn indicators but instead, cut off a short piece and affix it to my leader using a variation of the Open Loop or Two Loop Method of attaching a yarn indicator. My way is slightly different and easier than what I’ve seen posted on the Web, doesn’t kink the leader and is easily removed.
If I am using it as an indicator, it lands softly and because I have it in florescent yellow, orange & black (yes, black) I can work around situations where water glare or sunlight effect visibility, also a plus when using it as a sighter.
If I use it as a sighter, because of the way I attach it, I can put it anywhere on my leader including on the butt portion of any leader, including furled. Sometimes I use it as both an indicator or a sighter depending on where it is placed on my leader. If you keep it small, it isn't overly wind resistant so casting is essentially unaffected no matter how you use it.
I choose the method depending on the situation. On smaller waters, approaching a deeper run from the side is often a disadvantage and spooks fish or is impossible so I tend to cast directly upstream. At places like that, I also am fishing shorter rods and a high rod tip is often problematic or limits the distances you can cover. This is when I find an indicator an advantage.
In the “what's old is new" department, I also fish Tenkara style using level lines, which in my case is nothing more than a fixed length of florescent fluorocarbon fishing line with a tippet ring on the end. In Tenkara, the entire line becomes the sighter and the long rod & reach make it a VERY effective way to nymph.
Back when I first started fly fishing in the 1980’s, I also used to tie my own leaders using Golden Stren as the butt section. I may go back to doing that with 3X which seems to be the size tippet material I often tie in below the tippet ring on my furled leaders.
Interesting video, thanks!