If you are using a one-piece gasket, a small bead of silicone sealer on the top of the end seals and a slightly more generous bead on the bottom of the end seals will generally suffice. Lay up everything dry, to see how it all looks. That will tell you where you will need to use more or less sealer.
I've successfully sealed up motors with no rubber end seals used, at all. Toss in the side rail gaskets, bolt on the pan and then stitch in the front and rear openings with silicone sealer.
The trick to remember is cleanliness is next to Godliness. Silicone sealer will never work on an oily surface, so be sure the timing cover and rear main cap are bone-dry clean. Use acetone or brake cleaner, to make sure you have managed to clean off all the oil.