Best late war German arty for counter battery?

[MikeD]

So I'm a late war German guy playing my own long camaign against the Russians.
I've upgraded and expanded my core to it's fullest potential and am doing pretty well at holding my own, even when the Russians outnumber me by a great deal.
I've get little to no option to buy spotter ac. But, I do have several elite arty observers.

In delay or defend scenarios I use my battle points to buy offboard artillery since I've got plenty of Nebelweffers in my core.

My problem is I keep getting hammered by offboard Russian artillery.

My off board choices, usually the 15.5 cm battrie, will counter battery fire at the Russians once early in the game and then not fire again, but the Russian batteries keep hammering me and my smoking 'weffers into the mud.

I know.. welcome to the late war Eastern front.. move the weffers.. With a core of Panthers, King Tigers and Panzerknackers.. I've got no spare slots for prime movers.

Anyone got any thoughts on 'best' counter battery German artillery? Fastest turn around time, most damage /disruption done, etc..

Mike