I HAVE A HOUSE THAT IS 30 YEARS OLD. I am replacing the tub/shower door and want to regrout the entire shower with newer grout that won't get mildew. GROUT TOOLS DON'T SEAM TO BE GETTING OUT THE OLD GROUT IT'S REAL HARD IN PLACES. ALSO, DOES ALL THE OLD HAVE TO COME OUT FIRST BEFORE YOU CAN REGROUT?? IF SO I NEED SOME SUGGESTION ON HOW TO GET THE OLD OUT.