I'd recommend against the cast net - they tend to catch gill plates, etc. and damage fish. At least, thats my experience from catching baitfish for salt flats fishing...
I'd go wtih the seine, or even a length of the smallest diameter "super line" you can get at wally world (aka diseased fish mart), and a #16 or smaller hook. May need to buy a micro sized trout fly and remove the fly part of it. Mash the barb down good.