It's easy.

Step 1) Tie your mainline to a banana weight.

Step 2) Tie a mooching leader (can be purchased almost anywhere if you've not the inclination to tie your own,) to your banana weight. The bead chain side...

Step 3) Put on a plug-cut herring. This is the hardest part, but there are many tutorials available so I won't go into it here. You can use a cutting guide, and then experiment with various riggings until you get an attractive roll.

Step 4) Drop your rig over the side of the boat, and freespool it down as far as you feel like.

Step 5) Reel up your dogfish.

Repeat as necessary.