sometimes I would turn the wrong face around while fixing the edges.
I have 3 tips for you about the edges (I am assuming the "standard color scheme DFRBLU=WRGOBY so White on Down, Red on Front, Green on Right)
1) Edges that have yellow on them belong in the Up-layer so only focus on edges without yellow to put them in the middle layer
2) Make sure your edge is not "connected" to its middle layer face
3) Turn that middle layer face that can connect to the edge so your "working corner" goes to the U-layer, connect the edge by turning the U-layer, undo your first move. Because this is a bit theoretical, I will describe two cases for the FR-edge
3a) Example-scramble: F' U2 F. The non-U-color of the edge (red) can be connected to the Front-face. This means we have to turn the Front-face in a way that puts our working corner in the U-layer (F'). Now we turn the U-layer to connect the edge to its face (U2). Finaly we undo the first move (F)
3b) Example-scramble: R U2 R'. The non-U-color of the edge(green) can be connected to the Right-face. This means we have to turn the Right-face in a way that puts our working corner in the U-layer ®. Now we turn the U-layer to connect the edge to its face (U2). Final we undo the first move (R')
3c) Example scramble (advanced!): L F U F2 U2 L'. Your working corner is now at the DLB position and you want to put the edge that is now in the FU position into the LB postion. The non-U-color of the edge (blue) can be connected to the Left-face. This means we have to turn the Left-face in a way that puts our working corner in the U-layer (L). Now we turn the U-layer to connect the edge to its face (U). Final we undo the first move (L')
I hope this helps and Erik is right. When I switched from a beginners method to working corner, my times increased by 10 seconds, but that only took 1 day. 2 days later, my times were 5 seconds faster than before.