document little trick for those who read :)

Author: amaloteaux

documentation/modules/exploit/windows/local/bypassuac_fodhelper.md

@@ -15,7 +15,10 @@
 ## Usage
 
   You'll first need to obtain a session on the target system.  
-  Next, once the module is loaded, one simply needs to set the ```payload``` and ```session``` options.  
+  Next, once the module is loaded, one simply needs to set the ```payload``` and ```session``` options.
+  The module use an hardcoded timeout of 5 seconds during which it expects fodhelper.exe to be launched on the target system.
+  On slower system this may be too short, resulting in no session being created. In this case disable the automatic payload handler (`set DISABLEPAYLOADHANDLER true`)
+  and manually create a job handler corresponding to the payload.
 
 
 ##Scenario