Low water is certainly a challenge, especially ice cube cold winter low water. I agree with your description of fish holding in the heads of pools in broken riffle water. I've also found them tight to any overhead cover, in the snags, and in those difficult to fish, protected spots. Another technique is to fish small plugs or planers (from a boat or carefully wade) above such broken riffle water. An important ingrediant for success is to start the process well above the spot you think the fish hold and to be in STEALTH mode. Often the slightest bang, splash, or bonk will have negative effects on your chances to hook o.mykiss. Often these fish are "stale" and a change of pace (ie spoon,plug,etc. as you suggest) will trigger a response--no doubt about it, low water steelhead are a challenge.