I use the applicators that come with the shadows, and buy extra ones that can be found with the sponges - also like a dollar a package. There’s usually plenty of space in the tray for at least one extra applicator. Maybe because I’ve been doing makeup for so long, I take the tips they give on tutorials, but I don’t have any issues layering or blending without brushes. Just the applicators, loading or not loading them with whatever amount of coverage, using the back of my hand to blot and finger to blend, and apply mostly dark to light. I also line my eyes first, not last like a lot of them do. It’s too harsh a look for my age, plus especially with liquid liner, doing it first eliminates redoing my whole damn eye if I make a mistake. But I’ll always prefer blended edges with any liner, including the black liquid when I use it (Almay, btw, for that).
I’m not against using brushes, they achieve a nice look and seem easy enough to use, I just know myself and adding trying to keep them clean to my routine just won’t happen after it’s been something I haven’t needed to do since 1984, you know?
As far as YouTubers I’ve watched, I haven’t subscribed to anyone, but have watched more than a couple from Lauren Curtis and Julia Graf. The others I’ve watched have been in conjunction with product review searches. I watch their review of whatever I was looking for, and then watch other tutorials of theirs if anything looks interesting in the sidebar. I’ve also watched some drag queen tutorials to learn tricks that I can integrate into my full face dress up look (which only happens every couple of months!). I’ve been playing with contouring a little.