I tried several brands until 505. In my experience, 505 is better than all the others. A new one out that is supposed to be even better than 505 is Therm-O-Web Spray n Bond, but I haven't tried it. I was able to buy 505 locally only once; usually I bought the big can online from sewforless.com . I see they don't currently have the big can, but I have used the small can too:
http://www.sewforless.com/item/505_T...OUND_ONLY/1227