If you want Green Sunfish for bait .... the easiest/fastest way is to cast a Road Runner along a rocky bank, keeping the bait either landing or running within 1ft of the shoreline. (I catch them all the time when casting for Crappie & the Road Runner lands too close to the shoreline )

Casting a net for near surface running Shad is not too difficult .... getting the net down to deep running Shad is much harder. And I wouldn't recommend a 6' diameter net for deep running Shad ... you'd be better served with at least a 10' diameter or larger net & something in the range of 3/4" mesh (for the larger Shad). I say that because my 3/8" mesh net would catch 3-4" long Shad, but most of them were hung up in the mesh (& many escaped before getting the net in the boat). The bigger nets will have a lot more pounds of weight on them, too, which helps the net to sink faster. And you have to understand that even though the diameter of the spread out net is 6' or 10' or whatever .... once it starts sinking that diameter shrinks somewhat, as it turns into an upside down bowl shape as it sinks.

I originally bought my 3/8" mesh net to catch Shad to fish for Hybrid Stripers ... bought a smaller 1/4" mesh net to catch smaller Shad for Crappie fishing. I think I got the 3/8" mesh net at Wal-mart, but I got the 1/4" mesh net from Nylon Net Co in Tenn. (because local stores didn't carry the smaller mesh nets). But, I think the company is now called Memphis Net & Twine (I couldn't get on the Nylon Net Co website)
( https://www.memphisnet.net/category/cast-nets )

Also note : they advertise the nets as being X number of feet in RADIUS & not by diameter ... so a 6ft radius net would spread out to a diameter of 12ft. (My nets are 3ft radius - 6ft diameter nets)