OSX El Capitan - cannot make bootable usb stick with boot camp
If you find no option to select your external USB drive as an ISO target - are instead directed to install on your repartitioned hard drive immediately - open the info.plist and add your model identifier to the following:

&lt;key&gt;ExternalInstallOnlyModels&lt;/key&gt;
&lt;array&gt;
    &lt;string&gt;MacBook8,1&lt;/string&gt;
    &lt;string&gt;MacBook9,1&lt;/string&gt;
    &lt;string&gt;MacBookAir7,1&lt;/string&gt;
    &lt;string&gt;MacBookPro11,5&lt;/string&gt;
&lt;/array&gt;