Kent Cooper has come up with a very nice routine for drawing flexible conduit or ducting. The image below illustrates how the command works with various object types. If you use an existing object for the path, you can choose to delete or retain the original object.  The header in the LISP file explains many more options such as the ability to repeat the command on the previous path with different options. After you load the LISP file, type in the command FLEX to get started.