You always going to be looking at a custom build or extension to manage your Varnish cache - if you are making changes to products or categories with any kind of regularity I can't imagine your Varnish cache is particularly easy to manage.
I would say definitely look at the available extensions that are out there. If you are only after a Varnish cache then you might want to take a look at Turpentine which is not one I have used but is a popular choice and is actively developed. There are also paid version of similar extensions but not sure how actively they are developed, have a look on connect.
If you want to try a full page cache extension then there are a lot of options out there, some new, some more established. My advice would be to look at the more established options which are still actively developed - Magento full page caching is a complex area so an extension that is new to the market could well have bugs and probably is less of a complete caching option. There are also free FPC extensions out there like the popular Lesti_FPC however don't expect the kind of performance you might expect from a paid solution.
I'll leave you to look at the various options out there, read reviews etc, but I think I'm right in saying that our caching extension Evolved Caching is the only one which provides it's own FPC and also integrates directly with Varnish. It's likely with any other option you would need to go with either FPC or Varnish, but not both (not sure both a FPC and separate Varnish extension would work happily together).
Evolved Caching automatically invalidates and recreates both it's own, and the Varnish cache when saving cms, product and category pages in admin so your cache should always be up to date. This removes the need for a daily crawl of the site to update the cache which is often required with other setups. You can also cache to Redis, Memcached, APC or files, and we offer a free 30 day trial.