Both maximum and minimum inbreeding cause major selection problems if continued over many generations - moderate inbreeding gives best results. Maximum progress requires a mating system that provides adequate selection and a subtle balance between maximising inbreeding and minimising the loss of useful genes - usually approximating the inbreeding in cousin matings. Neither avoid nor enforce close inbreeding let the selection process find its own optimum. Mate best to best - ignoring relationships whether close or remote. Select using total scores that include all important qualities especially fecundity and viability.
Unscored qualities tend to change unpredictably.
Score both sexes. For the best results use breeding methods adapted to total numbers available. Optimum methods vary with each history of previous selection aims and inbreeding - similar past selection with moderate inbreeding improves resistance to new close inbreeding. Don't spread limited resources over too many breeds, varieties or strains - too small numbers slow progress and suffer from unpredictable chance effects. This method is practical only for the very largest breeders.