Generally speaking (or at least initially) I'm not a plug-in freak when it comes to animation. It's only once I'm happy I could do something without relying on a plugin, and usually after battling on for longer than I really should without using a plugin, that I finally decide go take the plunge and find something that helps me out/speeds things up (I just like to know how things work before I rely on them!).
Here's a perfect example - Overlapper 1.1.2 by Dmitrii Kolpakopv (for Autodesk Maya).
If you were to show what it does to anyone vaguely experienced with animation I'm sure they could tell you what they would do to get the same result - but it's the ease with which it lets us do it that makes it so good (and it has just enough options to cater for most situations).
Check the link to get a very good overview of its capabilities - but if you want them summarised in a few words it's: overlapping action (I know - who'd thought it!), flexibility, offsetting, delay, follow-through (no - not that sort!)....wibbly-wobbly-ness, wavy-gravy, floaty-boaty-coaty - I could go on but I'm sure you get the idea and things are getting silly.
Yes it's one you have to pay for but it's only the price of a decent bottle of wine and a burger (that's now I evaluate most things) so you shouldn't lose sleep over it - you should get more sleep - this'll make animating those creature tails super easy!