Which hair extension technique is better - using wax or sewing them together?

Plucking (tweezing), Shaving, Depilatory creams and Waxing are temporary hair removal methods.

Waxing usually lasts for 3 weeks, but it is painful.

Electrolysis and laser hair removal are "permanent" hair removal methods but are expensive and you have to find a trained professional, otherwise your skin could be damaged.

A review of the various hair removal methods is available at http://tinyurl.com/ob6tt

Which hair extension technique is better - using wax or sewing them together?

You should sew them because if you use wax it will take you hair out when you try to take the extensions out.