The polynomial \(2x^3 + ax^2 + bx - 4\), where \(a\) and \(b\) are constants, is denoted by \(p(x)\). The result of differentiating \(p(x)\) with respect to \(x\) is denoted by \(p'(x)\). It is given that \((x + 2)\) is a factor of \(p(x)\) and of \(p'(x)\).

(i) Find the values of \(a\) and \(b\).

(ii) When \(a\) and \(b\) have these values, factorise \(p(x)\) completely.