Einstein and Herbert both have external bias points, where you can easily access test points and do it yourself. VH4 doesn't (it's the first Diezel amp, I think Peter added this standard feature on later models only)
I recommend you get a Weber Bias Rite. It's fool proof and has the great advantage that you can check each tube individually (you can verify whether your set has been properly matched).
Even with the Bias Rite, be careful not to touch anything in the amp guts, it might well be the last thing you do as there are huge voltages (even after switching off an unplugging).
