Cosmo,
Try a larger eyepiece and no Barlow to start with. Find your target that way and then introduce the Barlow. You will find the focus to be well out as you have doubled (or whatever "times" barlow you use) the focal length.
Once you have your target focussed, then go for the 6mm and refocus.
You will have to work to keep your target in the eyepiece though! 6mm plus a Barlow is perhaps too zoomy
for Venus...
Stu