  The Colebrook equation $\zeta$ is implicitly given in respect to the unknown
flow friction factor $\lambda$; $\lambda=\zeta(Re,\epsilon^*,\lambda)$ which
cannot be expressed explicitly in exact way without simplifications and use of
approximate calculus. Common approach to solve it is through the Newton-Raphson
iterative procedure or through the fixed-point iterative procedure. Both
requires in some case even eight iterations. On the other hand numerous more
powerful iterative methods such as three-or two-point methods, etc. are
available. The purpose is to choose optimal iterative method in order to solve
the implicit Colebrook equation for flow friction accurately using the least
possible number of iterations. The methods are thoroughly tested and those
which require the least possible number of iterations to reach the accurate
solution are identified. The most powerful three-point methods require in worst
case only two iterations to reach final solution. The recommended
representatives are Sharma-Guha-Gupta, Sharma-Sharma, Sharma-Arora,
D\v{z}uni\'c-Petkovi\'c-Petkovi\'c; Bi-Ren-Wu, Chun-Neta based on Kung-Traub,
Neta, and Jain method based on Steffensen scheme. The recommended iterative
methods can reach the final accurate solution with the least possible number of
iterations. The approach is hybrid between iterative procedure and one-step
explicit approximations and can be used in engineering design for initial
rough, but also for final fine calculations.
