beerzebub is for after-cast delay not for casting time
but in your case i think you do this one:
1st goto src/map/skill.h look for #define RENEWAL_CAST change it to #define NON_RENEWAL_CAST
2nd compile it
3rd SET YOUR SKILLS.CONF castrate_dex_scale: 150 I THINK ITS 150 BY DEFAULT
4th edit the skills that you want to reduce cast/delay in this db/skill_cast_db_RENEWAL.txt (you can skip this step if you dont want to change any cast/delays)
5th run your svn then test your adjustments