ok.... I will try and explain this..
1. stretch a piece of tape from one end to the other with the top edge of the tape as your body line.
2. Next apply filler across the top and slightly over the tape...
3. now work that filler down making sure you are using the correct angle... you will have to tilt your board here... it wont be straight up and down.... Dont eat up the tape, try and just work the top filler
4. Now tape the top with the bottom edge of the tape on the new edge you just created.
5. Apply filler to the bottom now and again slightly on the tape edge... work that filler accordingly...
The key to this whole process is getting either the top or bottom right and then working out the other one... I will try find some pics of a quarter I did earlier this year