Can you focus on the location of your third eye while going to sleep so you enter a lucid dream?
yes
That will probably keep your attention on your body, though.
think of these energy centers not as actual "energy vortexes", but rather as thought-form representations of qualities of consciousness.
for example, when you focus on the third eye, what comes to mind?
use that.
it's about learning what your mind is doing when you are partaking in the activities and replicating it.