How to decrease on the knit side when it is th ewrong side of the work

Ok,
I am doing the Michael Kors sweater listed in my signature line. It is a classic cable-knit/aran-style sweater. So the borders on each side are purl (reverse stocking stitch). It is time to decrease a stitch on each side for the waist shaping (I have to decrease every 12 rows). But it has me decreasing on an even row or WS of the work (which is actually the stocking stitch side). So how do I do a decrease on the wrong side (knit side) of the work so that the extra bump of the decrease doesn’t appear on the RS (purl side) of the work? And which stitches do I do to get it to “slope” the correct way?

Thanks!
V.:??

Usually a p2tog at the beginning of a row, with a ssp at the end.