alot of people use different things.. I personally like to use "crud" from another tank and sprinkle abit of flake food in every day until the cycle is complete. Some will toss a piece of shrimp, ect. Essentially you want something to start decomposeing, and bacteria to start growing. The adding of crud from a cycled system is like adding a "bacteria starter" which some are more reliable then others.. but aquarium crud is free! You can also jump start a system with bio-media thats been pre-seeded in another FW aquarium, or ask your local LFS for a used peice of their filter floss ect.
These will all give you the same results in varying times ect.
And yes you can use a Algae scrubber set-up on a FW system. I keep live plants in most my systems with the same concept. depending how yours is designed switch out SW macro's for FW. I've even seen a few that the owner has intigrated houseplants to utilize the nitrates and grow them. or as simple as algae grown on river rocks in a stream-type set-up.
Another big difference is FW you will be wanting to do 25% WC weekly if not more depending on your stock. Most SW enthusiests I know do the whole Jaw drop... So invest in a good Syphon, at that size def look into the Python type, many brands available and they can be "home-made" as well. You may also look into a drip system ect..