2 bad edges: r U R' U r
4 bad edges: r U r
6 bad edges: r' U' r2 U r
Average movecount: ~ 11
Average double turns: ~ 3
Algorithms: 4
The edges marked green in each diagram are oriented, and the edges marked red are misoriented. An oriented edge is one that can be solved between its centres using only a combination of U, D, R and L moves, without regards to the rest of the pieces; a misoriented edge is one that cannot fulfil this criteria. For each possible number of number of bad edges after first block, the cube needs to be set up to the corresponding case using the [r2, R, U] moveset (while stuff like r U2 r is allowed, it usually is not necessary). Note, it is important that either the bottom or the top centre is on the U face. Following the algortihm, the DB and DF edges (or simply, BF) need to be solved, again using the same moveset.
Note that the final two moves are flexible and can be one of (U r), (U' r), (U r') or (U' r'); all these will solve the EO case. The choice has to be made based on which algorithm will result in the easiest BF case, or to preserve some block that can be utilised in the 2-gen part of the solve. As a rule of thumb, the last move should be such that the bottom centre ends up in the top, and the second-to-last move should be such that a BF edge connects with the bottom centre if possible.
The solving of BF is fairly simple and intuitive, and should take only 3-4 moves on average.