Slide ring finger problems, please technique

I am studying this lesson blues http://www.guitartricks.com/lesson.php?input=13277&c_id=16&ch_id=95&s_id=801 and I lack autonomy for the ring finger when I slide, I were to say I would appreciate any technique.

Thank you.

Hi, This one takes a little practice for your finger to get used to working separately from the rest.

Since this is a stretch, you may try the same slide one fret closer to the index finger, just to get used to the motion. (it won't sound very good) Your finger will naturally want to spring back into place.

Once you get used to this, try it as it is in the lesson.