Here I outline a few common methods in Judo for finishing the straight arm bar. These are mainly best suited to gi based grappling and so many of them may not be applicable to MMA or no gi BJJ.
This is not a comprehensive list or the be all and end all of methods, however, hopefully it may include a few ideas that people find useful.
Straightening the Arm
In addition a special on the secret to Neil Adams' famous Juji gatame turnover and how the key to the technique is hidden in plain sight.
Neil Adams' Juji gatame roll