You can use forceps to plant in gravel, sand or dirt, you can use the finger & crater method you described, you can use 1-2 drops of super glue gel to attach a small rock to the plant root to weight it, then just carefully drop it on top the gravel or soil. If the plant comes in a small planter in rock wool you can just drop the plant -container-rock wool into your tank. As you practice and experiment you will find different things work better for different plants.
My experience, using mostly pea gravel and larger gravel (1-inch) for substrate is that val, amazon swords and crypts with good root systems are easiest to push in, then drag a bit, with or without tweezers, because that helps spread out the root system under the substrate. Anubias works best with a few roots (not rhizome) pinched between rocks or buried under the gravel, or glued to a rock or piece of wood (cholla wood will almost dissolve out from under the plant leaving it kind of floating but anchored. Swords or crypts with almost no root system work best with a small rock glued to the side of the root/stem spot then set on top the gravel - roots grow faster and grow down into the gravel to anchor it and you don't risk the plant getting buried too deep and rotting.
Most important is to do what is easiest for you, experiment and have fun.
Good luck.