Being the spray maker that i am, i will say that there truely is no way to make a high quality animated spray. This is because there is a filesize cap on sprays and after 5-6 frames with a standard 256x256 spray, you will already have exceeded it. The reason SprayR is producing low quality sprays is because it was probably programmed with that filesize cap in mind, therefore reducing size and quality in order to add additional frames. So, depending on the size and length of the .gif you are trying to convert, you may not be able to create your spray.

However, if you send me the .gif, i could take a shot at it anyways :P