Beags,
Surely to correct IAS to TAS at lowish level (a few thousand feet) one merely multiplies the NM per minute that you're flying at by the thousands of feet you're flying at and subtract that from your desired TAS to reach your IAS.... or something to that effect... seem to remember doing something like that in the days before I solely flew at low level or high level... One can then use ones clock face rule to relatively accurately calculate your necessary heading and IAS to achieve track & TOT (or revise your eta).
Still wind planning and no need to ever touch the confuser (haven't even touched it since EFT Groundschool, found it in the bottom of a box whilst re-orging my loft the other day!) Never seen anyone in my neck of the woods using one!