I've been using un-insulated barrel connectors for the last few years. I started usage on my motorcycles when I started to find failed soldered connections that aged hardened and broke due to vibration. This is normally not the case for our cars but the barrel type are very handy to use without soldering. I cover them with normally two layers of shrink tubing.
The RTL crimper and dies I bought here:
http://www.vintageconnections.com/Products
http://www.vintageconnections.com/Products/Detail/94