More practise Bob,

Pretty much you steer down as soon as you feel the gust coming and you head up again as soon as you feel the gust falling away. Halve a second to soon or too late and the spi will either pull you over or collapse. After a while you get the hang of it. Don't wait till the gust has hit, you must make corrections and be largely finished with them before the actual gust hits.

After a while it become second nature to do this right.

Wouter