ASP.NET MVC 3 client-side validation with parameters

Following on from this post Perform client side validation for custom attribute

I am trying to get my head around how to do this, passing additional parameters to the client-side script

As I understand it so far to implement custom validation with MVC 3 the following is required

Create a custom validation attribute

Based on ValidationAttribute and implementing IClientValidatable. I have also see some examples deriving from ModelValidator, which seems to implement the functionality of both ValidationAttribute and IClientValidatable. So this is my first point of confusion as to what the diffirences are or whether ModelValidator was used in MVC 2 but is now deprecated or what ?

An instance of ModelClientValidationRule must be returned from GetClientValidationRules() to specify details such as the error message, ValidationType (which I understand to be the name of the Javascript function that will perform the client-side validation) and any additional custom parameters that the attribute may have, and that need to be passed to the Javascript validation.

I assume that the runtime (not sure which part of it) then use the ModelClientValidationRule to generate html attribute in the tag elements as follows:

data-val="true"  (to indicate that the element requires validation)
data-val-[ValidationType]=[ErrorMessage]
data-val-[ValidationType].[ValidationParameters(n).Key]=[ValidationParameters(n).Value]

Implement the client-side validation logic

A Javascript function must be created and added to jQuery.validators with jQuery.validators.addmethod() so that JQuery is aware of it when it need to be executed. Something like:

jQuery.validator.addMethod(
    'greaterThan', 
    function (value, element, params) {
        /.../
       r