  We present the extension of two general algorithms for the treatment of
infrared singularities arising in electroweak corrections to decay processes at
next-to-leading order: the dipole subtraction formalism and the one-cutoff
slicing method. The former is extended to the case of decay kinematics which
has not been considered in the literature so far. The latter is generalized to
production and decay processes with more than two charged particles, where new
"surface" terms arise. Arbitrary patterns of massive and massless external
particles are considered, including the treatment of infrared singularities in
dimensional or mass regularization. As an application of the two techniques we
present the calculation of the next-to-leading-order QCD and electroweak
corrections to the top-quark decay width including all off-shell and decay
effects of intermediate W bosons. The result, e.g., represents a building block
of a future calculation of NLO electroweak effects to off-shell top-quark pair
(WWbb) production. Moreover, this calculation can serve as the first step
towards an event generator for top-quark decays at next-to-leading order
accuracy, which can be used to attach top-quark decays to complicated
many-particle top-quark processes, such as for tt+H or tt+jets.
