I have heard of some guys fishing frogs in that stuff but I would prefer to use a flipp'n bait. I would imagine you would get a lot of blow up with little hook up's. Also being further away from the mat with a frog you would have a much great chance of not even being able to get the fish out. Lets put it this way that big fish would have been just a fish story if I had it on the frog.

As far as knowing what holes are key holes comes down to 15 years of delta fishing experience. Its kind of hard to explain but I will try. I prefer the hol on the back side of the dock's at its deepest point with current moving under it but not moving the hyacin. Then I look for a pilon that supports the dock. Now picture fish face 1st into the current using the pole as a current break under they under the hyacin. I also prefer the fish's hiding spot to not have a hole to flip into, the harder it is to get the bait in there home the better chance there is one waiting underneith. That is the perfect spot, its got extra oxygen some depth a current break,shade and they can sit and wait for food.

The bluegill is made by 3:16 lure company. Get yourself one but after Rancho :) here is a link that should help

http://www.tacklewarehouse.com/descpageSWM316-MFBG.html