its not so much the sealant but where you put it. when u put the gasket down make sure its is a nice fit into the corners of the front cam bearing housings, then apply a blob of sealant to the corners and then put the half moon seals in place.
tighten down the cam cover evenly and watch the half moon seals compress. dont over tighten the cover as the gasket will spread. a good nip when they are tight will do.

if its still leaking it is possible that the oil could be comming from under the corner of the cam housings themselves, if they were off at any stage it is possible that there was no sealant placed under their base and unless its was done oil will seep out big time. it important that this is done.its specified in the workshop manual, and it did my head in (as in brain) a good while back