Note: Hold Colour B (held double) and Colour A as if to work stranded colourwork stitches, with Colour B travelling below Colour A on the wrong side of the work. Only insert RH needle into the space between stitches (not into a stitch), go under and behind the Colour B loop from an earlier row/round (if applicable). Do not tension Colour B too tightly, making sure the pulled loops do not gather the fabric. When working the pulled loop and the next stitch together, insert RH needle into the Colour B loop as if to knit or purl as usual and work the loop and the stitch together with Colour A.

PUL3L2B

Locate the space between the 3rd and 4th st on the LH needle, insert RH needle into 2nd space below the just located space. Knit into this space with Colour B (held double) as usual.

PUL3L3B

Locate the space between the 3rd and 4th st on the LH needle, insert RH needle into 3rd space below the just located space, going under the Colour B loop from an earlier row/round (when applicable). Knit into this space with Colour B (held double) as usual.

PUL3L4B

Locate the space between the 3rd and 4th st on the LH needle, insert RH needle into 4th space below the just located space, going under the Colour B loop from an earlier row/round. Knit into this space with Colour B (held double) as usual.

You can find Valerie's videotutorial here.