Here is an easy way to ask for a stumble by email or on a post.

I just published a blog carnival for a client and sent an email to each person that was published. I told everyone that that the carnival was published and I asked that they stumble the post for more exposure.

Using this type link: Asking For A Stumble opens a StumbleUpon window which looks like the image below (if the user is logged in).

Here is the format in case you want to reuse it:

http://www.stumbleupon.com/submit?url=http://cheapkeywords.info/asking-for-a-stumble/&title=Asking%20For%20A%20Stumble

In case you don’t know:
the 1st part: (http://www.stumbleupon.com/submit?url=) is the SU site.
the 2nd part: (http://cheapkeywords.info/asking-for-a-stumble) is your link.
the 3rd part: (&title=Asking%20For%20A%20Stumble) is the title you associate with your URL.

Stumble if you will. Use the link if you like.