I just went through a similar problem. I got a new brand of PLA "3D Solutech" and ended up using about a 1/4 pound of the stuff trying to stop the stringing. The biggest factor was "Retract and Prime" length. I am using Craftware not Simplify so not sure where the settings for it are in Simplify. The default was 1mm retract and prime. I had to up it to 2mm to get the stringing under control. Also lower your temps as low as you can. I am running this stuff at 195C. Slower print speeds also help.

Scott