Lava casting is very situational, absolutely. However, you don't have to continually place water for smooth stone generating.

To do it automatically, place a row of 7 horizontal pistons, with a row of your own stone on their faces. Place two water sources on both ends of the stone row and place a single lava source block on top of the center stone block. Also place blocks to contain the water on the other three sides, and blocks to contain the lava but that allow it to spread across the top of the whole row of stone.

Put the pistons on a clock. I forget the delay right now, about a half second should be fine though.

The pistons retract when our clock unpowers, and water spreads a lot faster than lava, giving the water a chance to flow under the lava. Then the lava ticks, creating a row of 7 stone out of the flowing water. Then the pistons power, shoving the row out, and the extended pistons hold back the liquids. Repeat.

The result is a 13x7 sheet of smooth stone. Sit sideways so you mine rows, not columns. It generates faster than you can break it unless you have a setup to instamine it, which still makes it faster than anything else. Add silk touch if you want smooth stone, or don't and just enjoy faster speeds.

Faster than cobble by a lot, faster than natural mining because you don't have to move, and while technically AFK'ing isn't faster, it feels faster.