Map offsite SubDomain to MU subdomain on our Server (using Plugin)

Hi -

Thanks for a great service and plugin. We want to map an offsite subdomain to an MU subdomain on our server. We have installed the Domain Mapping plugin.

We want this to happen: blog.OFFSITEDOMAIN.com ::: maps to :::> subdomain.OURDOMAIN.com

I want to verify the correct steps here, then I have a couple of questions:

1. Set up a subdomain using the Control Panel (ie. blog.YOURDOMAIN.com) of the OFFSITE Domain.

2. Add a CNAME for the subdomain you create (ie. blog.YOURDOMAIN.com), using the control panel of the OFFSITE domain, and point it to the blog URL on our domain.

3. Add a DNS "A"record pointing at the IP address of our server using the control panel of the OFFSITE domain.

4. In the Domain Mapping field for the blog on our server, enter the offsite subdomain in the appropriate field.

* Is this the correct process?
* I read some other threads here about problems and am aware that hosting controls vary from host to host -- what should we be on the lookout to avoid in this process?
* Any other best recommendations to facilitate this process?

Thanks!