How to quick fire explosive gel on the ground

You need to restore the Comms Tower of the district you want to be able to fast travel to. Doing so will unlock the Batwing Drop Point to that area. You can tell if it is unlocked if the icon is white (as opposed to being red).

To fast travel to the location, hover over the drop point icon and choose fast travel option. I play the PC version so that would be Enter (by default). For the other consoles, that would be A on the Xbox 360 and X on the PlayStation 3.

Penguin's Black Market is a multiplayer-only feature. It allows you to purchase crates containing gear and other items for use online.

When you enter the store, you will be greeted with notifications that you have some crates and are given the option to open them. I don't think the items you get from the crates are predetermined, it appears to be random.