  Plane-wave backgrounds play a special role in strong-field QED as examples of
a non-trivial field configuration that remains simple enough to be treated
analytically whilst still leading to rich physical consequences. Although great
progress has been made applying standard field theory techniques to QED in
plane wave backgrounds, the calculations tend to be quite long and complicated.
Yet, both in vacuum and in constant backgrounds, the first quantised,
string-inspired "Worldline Approach" to field theory has a long history of
offering substantial simplifications and calculational efficiency.
  We present a new, general approach to incorporating plane wave backgrounds
into the Worldline Formalism that extends initial work using a semi-classical
approach by Ilderton and Torgrimsson (who also participated in LPHYS'21). The
method uses resummation techniques to take the background into account
non-perturbatively and yields "Master Formulae" for the effective action and
scattering amplitudes in the background. It is hoped that this may offer an
alternative tool to studying QED in plane waves that may streamline otherwise
complex calculations, as has been achieved in the better explored constant
field case.
