Also, flash drives are only good for so many writes. It would die MUCH faster using it as swap space/RAM.
If you need to make your machine go faster, the RAM, Processor, and Motherboard are the most important factors. Upgrading one of those will do way more than trying to use a flash drive. It's just not fast enough and would die too fast to be used very long.
If your virtual memory is too small, increasing that might give you a performance boost, but no hard drive has a faster access time than RAM. More or better RAM would probably be your best option to increase computer performance.