Lauren v. Intarsia: Round 1 - Seed St

I want to make a pair of arm warmers for a friend. She'd like cables on a contrasting background, i.e., via intarsia.

I've never done any sort of stranded knitting before, merely horizontal stripes. The latter nearly drove me crazy by the end of a 7" x 9" illusion-knit block so I couldn't imagine that dealing with multiple colors (and tangling strands) would be much easier. Of course, I was the one who suggested one-colored cables on a different-colored background, knowing full-well I'd need intarsia (moreover, at that time I'd planned on doing them up in the round; I've since given up on that idea and am most grateful that the pattern is already written for back-and-forth knitting).

I like pushing my limits, but I'm not one to begin on the hardest difficulty setting without first testing out the skills required--especially when someone else is the intended recipient so I'm striving for perfection more than normal. After the initial sighting, I've seen a few "monthly necessities" bags and decided to make one of those with a simple heart pattern on the front in a CC.

Shortly after beginning it entirely in stockinette, I frogged it and made 3 rows if seed st as the base to keep it from curling as much. From there, I thought, "it'd also seem prudent to knit the closing flap in seed st to stabalize that as well," which took me down a slippery slope to, "so long as I have that much seed st on the back, why not include some in the front, too? I'll do the heart in seed st!"

So now I'm faced with making my first-ever intarsia st as a purl on a knit background. My usual resources fails me ...well, they don't fail me completely (new mantra: "old over new") but they don't hold my hand through non-stockinette intarsia. As much as I hate to admit it, that's kind of what I need right now.

The best I've found from Google so far is this post on garter intarsia. It doesn't have anything about purls, of course, but it was encouraging to see the process someone else used to get creative with this method. She (He?) had to deal with strands being on opposite sides, which is kind of close to my predicament.

I've already tried a few times and either get the MC mixed with the CC or no purl bump, but I'm still determined to do this. Once I get that purl bump cleanly on the RS (and get it to stay there unlike that time it mysteriously disappeared after switching back to MC) I'm not going to be too picky about whether the strands were properly linked. It's one st and immediately going back to MC after that so any hole really wouldn't be that noticeable. In fact, it may even be remedied while weaving in the ends.

For now, I've frogged and ranted enough for one night. Tomorrow's another day.