In this paper we continue our systematic study of form factors of half-BPS operators in N = 4 super Yang-Mills. In particular, we extend various on-shell techniques known for amplitudes to the case of form factors, including MHV rules, recursion relations, unitarity and dual MHV rules. As an application, we present the solution of the recursion relation for split-helicity form factors. We then consider form factors of the stress-tensor multiplet operator and of its chiral truncation, and write down supersymmetric Ward identities using chiral as well as non-chiral superspace formalisms. This allows us to obtain compact formulae for families of form factors, such as the maximally non-MHV case. Finally we generalise dual MHV rules in dual momentum space to form factors.

We compute the two-loop Sudakov form factor in three-dimensional N = 6 superconformal Chern-Simons theory, using generalised unitarity. As an intermediate step, we derive the non-planar part of the one-loop four-point amplitude in terms of box integrals. Our result for the Sudakov form factor is given by a single non-planar tensor integral with uniform degree of transcendentality, and is in agreement with the known infrared divergences of two-loop amplitudes in ABJM theory. We also discuss a number of interesting properties satisfied by related three-dimensional integral functions.