The most specific exercises particular to Chopin's music were created by Alfred Cortot and published by Salabert. Whilst there is nothing specific to the Carnival of Venice variations, this piece is so similar to Chopin's Berceuse that you may benefit from the Cortot Volume 1 edition of Chopin's Diverse Pieces, which includes the Berceuse.http://www.sheetmusicplus.com/title/Diverse-Pieces-Volume-1/3173725?id=69435
It helps but is not essential if you read French, since most of these Cortot editions have not been translated into English. The printed exercises are so obvious, including the different fingerings, that the text is not critical. Cortot does a very good job of dissecting the technical difficulties of Chopin's music and breaking down the hard parts into exercises. On the other hand, he often requires you to repeat the exercise in all major and minor keys, which is a bit of overkill, so use your judgment regarding what you need.
The most critical aspect of any Chopin exercises is to develop a relaxed hand, with natural fingering and a complete fluidity of motion - Chopin called it suppleness. The most difficult technical challenges in his music are not really conquered until you can play them without any tension whatever. I know this sounds impossible with much of his music but it is the goal and allows you to concentrate freely on the musical elements.
The Carnival of Venice variations are often not well known and seem restricted to student assignments, when they should be played in concert halls by major artists. They are wonderfully musical in their own right and historically are yet another example of Paganini's influence on so many musicians who heard him perform. Even if you can't play these for public performance, they are worth having in your private repertoire for fun, so play them somewhat slowly if that is what it takes to enjoy them.