It depends on the relative height of the rain barrel and the point of use...most drip system rely on higher line pressures than what a barrel might provide
Look into a rainxchange system by Aquascape Inc. Collects runoff and can be custom designed for any situation/enviroment - www.aquascapeinc.com click on find a contractor. Certified Aquascape Contractors are trained in the correct installation methods of Aquascape Inc products and the products themselves are great!
I have done 2 systems for client's and use a slow drip system tied to 55 gal. drums.
Add a drain value to the system so when winter comes you can drain the barrels and keep them empty.