Formalin is not likely your friend in this case. FW dip is not likely going to be helpful either.
A 10gal tank will be helpful for future QT.
In my opinion, I would go that route and pick up what you described, but you can skip the light for now if you have enough ambient light for observation of spots, etc. Feel free to go with a light if the budget allows, as you will want to QT everything for observation prior to going into your tank later.
Pick up two or three PVC elbows(1.5" should do) and scrub them down without cleansers, remove stickers, etc. Put them in a pile and the clowns should take to them pretty quickly.
Be prepared for plenty of water changes, you are setting up for 6 weeks.
Good reading here:
http://www.petsforum.com/personal/tr...marineich.html