I have alot of luck with a lvl 3 flats right next to my city spam attacking with 100 or less pending the lvl of the flat. Attack, abandon, repeat. The method is to be persistiant about it. Send as many atttacks in an hour as you can. I also have had alot of luck with attacking lvl 1 - 3 with 1000 scouts. The true key to medals is persistence...