I just break the bead, pour it in, and reseat/reinflate. Not prehistoric, no big deal really.

I just unsrew the inner part of the valve (Schrader), use a bottle with a thin tip I've prefilled and squirt the goop it in via the valve stem, rotaring occasionally. Screw the stem insert back in, tighten and reinflate the tyre, I thought i was easy. How is it complicated?.

Don't they just have syringes you can use instead? That seems easier-er...

Just buy a stans no tubes refill bottle. 2 oz. Then keep refilling the sucker. Remove the valve core. If you're doing it the old school way it's way messier. The stans no tubes syringe was even messier.

I always seat tires before putting sealant in and this almost guarantees no splash back. https://sprocketkings.com/products/stans-no-tubes-regular-tire-sealant-2oz-bottles