There is no 'one size fits all' for douching. Yes it could be diet related but once you get your technique sorted that's not a problem it just might take longer, and sometime yes it is time consuming!!! You might have to douche and then leave it an hour and go back in and check again etc.
You can actually 'over douche' you basically push too much water up there and it goes too deep which then results in you making things deeper up inside your intestine start to move down! You only want to clean your rectum so don't put too much water up there. This video might be a bit of a help but you basically need to practice… and sometimes 'shit happens' even to the best bottoms 
http://www.xtube.com/video-watch/How-to-clean-your-Ass-Arsch-spuelen-15265461