How much usage is yoru vanity top going to get? If it is not a lot here is one or two things to try. I have used cocobolo qutie a bit in woodturning and in making small furniture and have had success with two different techniques.

1st (little or no rough usage on top). Start sanding! I like to use the no-load stearate from the sanding catalog. Keep sanding to finer grits, I like to get around to 600 or better with the no-load. Then you can switch over to a wet dry sandpaper and go to about 1000 using a lubricant. After that, go to pumice and then rotten stone and rub it in with a felt block or rag. You should be starting to see qutie shine now. The next step is to take some buffing compound, I like the dark rouge for the cocobolo, and work it in using a buffer. By now, if you have taken you time, you should be getting an abolute glass looking surface on top. The final step is to take paste wax and buff that in. I have used this technique on cocobolo bowls and it only needs touch up once a year with a little more paste wax. This gives you a mirror finish that shows off the cocobolo to its best.

The other technique is to treat the cocob9lo like teak and wipe it off with acetone before applying a finish to remove the oils, even this is problematic. I like to use shellac or laquer on top as it is faster drying and seems to aviod the oil problem. Unless you are using this as a high use surface with alcohol, it should work fine.

One word of warning, the cocobolo will darken with age unless it is an exceptionally red piece. No matter what it still is a beautiful wood though you need to take precautions as you can develop quite an allegic reaction to it over time.

I would suggest if you have the time, check out Bob Flexner's excelent book on wood finishing "understanding would finishing" as he breaks downthe mythos around finishing into simple science.

Good luck.