I read, that it is pretty important for beginners to do it out loud - I do it on my I-Phone recording function.
Did a second session - and maybe it was coincidence - but after a minute or so the second time - I was visualizing in a clarity and spontaneity I really usually don't have. Will go on with this! Definitively.
At one point I felt like describing a bona fide dream!

Oh yeah - and my source says, that it can be quite useful to listen to the stuff as well, once you have a moment, esp. after a while, when the images really come streaming and are not touched by intent.