Venting to the Air cleaner is a pretty good way to do it. You might want to check around at the auto parts stores and look at the different "breather" filters out there.
One thing that you might consider is the "breather" filter from a mid 90's VW 2.0L 4 cylinder. It has 2 approximately 18MM barbs on it and a barb on the bottom that would go into one rocker cover.
If your rocker covers have the "grommets" in 2 places on each cover the best way would be to put a breather filter in 1 corner, then run a hose from the same side other hole across to the VW "breather" in that grommet. Then the second barb run a hose to the air cleaner.
This has a couple advantages, you get fresh filtered air into the crankcase to replace the fumes, the VW breather separates a lot of oil and it drains right back into the rocker area and most of all its CHEAP!