Sprints for a distance swimmer

I've been mostly concentrating on events such as 400, 800 and 1500 f/s. So most of my training of late has been in improving speed endurance and stroke efficiency. I'm in an event on February 6 though where the only events I'll be doing are 50m and 100 f/s. Can anyone provide me with some suggestions of what I can do in this short period of time to improve my times in these two events? I'd like to beat 30 seconds and 1:10 respectively. My PB's(recent training and events a while back) are about 32 and 1:15. Typically my sprints have been rather messy. Thanks, David