  A practical approach is presented which allows the use of a non-invariant
regularization scheme for the computation of quantum corrections in
perturbative quantum field theory. The theoretical control of algebraic
renormalization over non-invariant counterterms is translated into a practical
computational method. We provide a detailed introduction into the handling of
the Slavnov-Taylor and Ward-Takahashi identities in the Standard Model both in
the conventional and the background gauge. Explicit examples for their
practical derivation are presented. After a brief introduction into the Quantum
Action Principle the conventional algebraic method which allows for the
restoration of the functional identities is discussed. The main point of our
approach is the optimization of this procedure which results in an enormous
reduction of the calculational effort. The counterterms which have to be
computed are universal in the sense that they are independent of the
regularization scheme. The method is explicitly illustrated for two processes
of phenomenological interest: QCD corrections to the decay of the Higgs boson
into two photons and two-loop electroweak corrections to the process $B \to X_s
\gamma$.
