Valve cover gasket installation
All valve cover and oil pan gaskets constructed from rubber should be put on dry. This includes cleaning oil from the surfaces of the cover and the engine before installation. I cannot speak for Elring, but in the case of Victor Reinz gaskets, if a sealant is needed, it'll be included in the package with the gasket. Both Victor Reinz and Elring are major suppliers to the OE European car manufacturers and in every likelihood, your BMW has gaskets on it made by both companies since OEM platforms are typically supplied, piece by piece.