Two-eyed needles - yes they have a use.

A fellow textiler sent me the following link about double-eye needles, which you may like to investigate.
http://store.dknits.com/pd-double-eye-needle.cfm

I have tried mine using two different yarns, a thick or novelty yarn along with a thinner tapestry wool; my result was not obviously two yarns, only on the bottom row could you tell and then the next row down that would be covered up.  However the overall result was quite nice, a variegated seascape was in my mind, and I used a piece of rug canvas from the Op Shop.

Seascape using two yarns at a time in a two-eyed needle

©Christine Linton