You need to practice them as well. You can't just memorize something once and then just recall it whenever you want as fast you want. Unfortunately, that's just not how it works. Here's what I did...take the first 5 (あ、い、う、え、お、 was the first five on the chart I used), write them down on a paper, reading them outloud as you go. Cover those up, and try to write them from memory. I don't you'll get them right the first time, so don't expect to know them after the first time
Uncover the first ones, and see how you did, and go back and do it again. Once you feel that you know those half decently, go on to the next 5 (か、き、く、け、こ...I think?) when you start copying these from memory, don't do just the 5 your on, make it accumalitive(sp?). Okay, I hope that made sense, this is what I used and it took me maybe about a week or so to learn them, so not too bad imo. Good luck!