I use Imperial for case forming and certain sizing tasks. Works great.
For most low-volume bottleneck rifle sizing, I use Hornady Unique. (Easier, cheaper.)
For bulk stuff, I grab a lanolin-based spray lube.
Just remember:
If switching lubes or using a die for the first time, always thoroughly clean the die first.
Some lubes don't play nicely together, and may result in a stuck case.