Gary, You do NOT need to use initBinder if you are using the ConversionService. I just stood up a Web app that is using the Conversion service and I don't use @InitBinding.
There are two basic conversion service factory beans.
1. ConversionServiceFactoryBean - This class sets up default converters for converting strings to basic objects. This class allows you to specify custom object converters. For example:
2. FormattingConversionServiceFactoryBean - This class sets up basic formatters for doing date and number conversions as well as setup default converters for converting strings to objects.
<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean" >
I extended the FormattingConversionServiceFactoryBean and added a setConverters method so that I can add my custom converters through the configuration.
So to answer your question. You specify your custom type converters within the conversionService bean configuration setup like the code snippet above. The conversion service will handle the rest for you.
Let me know if this did not answer your question.