Great response Jim! Great K factor article.

One way I practiced over the winter was lots of flights of just practicing lines. Straight through the box to an immelman straight across the top. Split S then repeat. Then big square loops and 45 's through the middle then repeat all inverted. Then add lots of half rolls, change turnarounds, etc.
The key is knowing were the plane is at all attitudes and all parts of the box. I also practice the sequence above or below the class I'm flying every so often to force me to do different stuff.