I was just painting some trims and used a trick that worked well for me. Like you, I found that with a brand new blade it's so damn sharp and pointy (giving almost zero contact) that it can wander out of the groove and you don't even know it's happening until it's too late. So I took an old blade which had a much blunter V in it, and a slight curve on the end of it (it's a #11, but they curl up a bit at the end as they age), and sharpened up just the edge on some very fine sand paper, ie, I did not make the V any finer, more like a boat with a flattish but sharp keel, and with the slightly curved tip. This blade tracked in the groove very well for me, much better than a super pointy new blade. I will make a dedicated boat keel blade for this purpose going forward
