If I use the ferber method, what do I do during growth spurts or teething?

There are Exceptions. The ferber method is fine as long as the baby has no other issues. For example teething can be painful and it is not the proper thing to do to not console the baby. When the baby has an illness, the same rule applies. Otherwise thismethod s a good one to promote sleep hygiene.
Camelia. Camelia is a homeopathic teething remedy widely available and very often helpful. You may be able to continue the ferber method by treating the teething this way. As far as growth spurts go...These occur so frequently in the first year as to be unavoidable.