the dash is quite tricky, but once you get the hang of it its quite useful. first turn into the bat. then you put the following comands
Hold down the X button.
then while holding down the X, in a quick circlular motion,on the D-pad go Up,up-left,left,down-left,down,down-right, then you must time this correctly just as you hit right, at the same time hit: Right-X. thats the last command you will put in. like i said its a tricky spell/move but practice and you will get the hang of it.
I hope I was able to help out alittle. Oh and the X is only going to hold Alucard still while he is in bat form. let me know if you got it to work.
http://i11.tinypic.com/4r2c21v.jpg