4 x 4
For all larger cubes I simplify them into a 3x3 then solve it like one.
To simplify them I start by paring up the centers. Then commute the edges together into sets.
There are a couple parity algorithms that you will need to know.
Dd R F' U R' F Dd'
Rr2 B2 U2 Ll U2 Rr' U2 Rr U2 F2 Rr F2 Ll' B2 Rr2
Switch Opposing Edges:
Uu2 Ll2 U2 l2 U2 Ll2 Uu2