I just did a project in which I had to align several kicks/snares for a layered-sample, Ed Banger Records style sound. Something that helped me tremendously was to use the Nudge left/Nudge right key commands, and then use my ears. I like to put the Set Nudge Value button and Nudge Left/Right in the tool bar (Ctrl+Click on toolbar>Customize Toolbar) so I can easily see what the Nudge value is, though I use the key commands for most of the actual nudging. Line the kicks up as best you can with the mouse, then set nudge value to ms and start adjusting. When you get super close set it to the sample for the finishing touch..