What are the key considerations when selecting a concrete floor grinder for surface preparation and polishing projects in the Los Angeles construction industry, such as grinding disc types, motor power, and weight distribution? Are there specific models or brands of concrete floor grinders that are highly recommended by professionals in the Los Angeles area for their performance and durability? How does the grinding process of a concrete floor grinder contribute to achieving a smooth and level surface on different types of concrete in Los Angeles? Can concrete floor grinders be used for other types of flooring materials, such as terrazzo or epoxy coatings, in the Los Angeles construction industry concrete floor grinder Los Angeles? Are there any recommended safety precautions or training requirements for operating a concrete floor grinder to ensure worker safety and optimal results in Los Angeles? Are there any reputable suppliers or distributors in Los Angeles that provide high-quality concrete floor grinders along with technical support and maintenance services?