It is frequently stated, for example on Wolfram Mathworld, that the general sextic equation
$$x^6 + a_5 x^5 + a_4 x^4 + a_3 x^3 + a_2 x^2 + a_1 x^1 + a_0 = 0$$
can be solved in terms of Kampé de Fériet functions - however the explicit solution is hard to find.
How can one solve the general sextic equation with Kampé de Fériet functions (or indeed other functions)?