A generalized, but simplified, kinetic equation for the distribution $F$ of a dust component in a plasma is derived in the seven-dimensional phase space $({\bf{r}},{\bf{v}},Q)$, where $Q$ is the dust particle charge. The equation for $F({\bf{r}},{\bf{v}},Q,t)$ takes into account charging, charge spread, collisions and an electric field. The charge $Q$ is considered to vary continuously. From the equation we find an analytic solution for the evolution of dust in the seven-dimensional phase space that shows collisionless diffusion owing to the combined effects of charging, charge spread and a constant electric field. We also derive a ‘vector kinetic equation’ of dust and subsequently a set of macroscopic equations, and show that the equations lead to a generalized classical diffusion of dust particles owing to fields and non-uniformities, collisions and charging, including charge spread, and to plasma wave effects including damping caused by charging and charge spread in the collisionless case.