I use the reinforcements around the bolt holes. They needed some slight modifications since they are meant for shivvies, but they helped. I have also had good luck using Superformance gaskets against the head with a cork/rubber gasket glued to them and against the cover. The cork tends to mash out around the thin head rail but the Superformance holds up there better. While the cork follows the contours of my steel valve covers better than the harder gaskets.

Typically Hemiroid, it takes $100 and a lot of work just to gasket the valve covers. And mine are pretty good, but are not bone dry.