This seems like a similar problem to running under AeT. The usual suggestions there are to find flatter or slightly downhill terrain or to use run/walk intervals to improve economy. I wonder if you could do the same short intervals to improve your skiing efficiency?
Scott usually suggests starting with 30 seconds of running (or in your case, faster skiing), then recovery for say 2 minutes. The short period of higher intensity is short enough it isn’t going to hurt your aerobic base. Then build up the faster/slower ratio over time and ideally you’ll end up being able to ski aerobically continuously.
That said I’ve never tried that with my xc skiing (but I am using the technique for running). I’ve noticed with time I can kick and glide a lot better under AeT just from putting in the hours of Z2 training. My xc course where I live is very hilly so there isn’t a lot of kick and glide terrain. But I have noticed I’ve gotten faster at the same HR by just putting in the hours, including many times where I had to go uphill in slow motion!