The performance of three different L-2 methods are tested in calculations of radiative association cross sections in collisions of Li with H+. The first two methods, the smooth-exterior-complex-scaling method and a method using complex absorbing potentials, are based on the direct determination of poles of the Green function and are superior at low collision energies where narrow shape resonances dominate. The third method, based on the iterative Chebyshev-polynomial expansion of the Green function, is efficient only at higher energies where the cross sections are smooth functions of the collision energy.