http://www.waytekwire.com/products/
Check out Weather Pack connectors. Sealing isn't really required for interior wiring, but they're handy to have around and very useful for general automotive stuff. If you're going to invest in the tools and knowledge for a connector system, Weather Pack is the way to go in my opinion. It's not the best, smallest, or lightest connector out there, but it's a good combination of cheap, easy to use, and easy to purchase in small quantities.
Pegasus has some nice instructions and they're a good source for small orders.
https://www.pegasusautoracing.com/gr...ID=WEATHERPACK