I've actually managed to defeat the grey tide twice - once about 20 years ago when I found mysefl between jobs (waiting for a clearance to come through), and then a few years later when I made the mistake of buying another 50ish minis for a game I never actually played.
A couple of things to consider: is your goal to get all the minis painted, or to get them painted well? Because the approach I'd take in each case is somewhat different (my goal was to get them all painted).
Either way, my first piece of advice is that you really must stop buying new minis until the old are done. Or, if you absolutely can't bear that, you need a hard-hearted clear-out of the minis you aren't ever going to get to.
Secondly, I agree with the advice to get organised. In my case that meant grouping a lot of the minis into large bands of 'similar' figures - the ones that would make up a coherent unit. (The special minis were then handled separately, but there were far fewer of those.)
And thirdly, you need to be consistent in allocating time - ideally, a bit of time every day, but failing that block off some fixed times for painting and try really hard to stick to those.
Once I'd done that, it was a case of dealing with the minis a block at a time, working through the layers one by one and just getting it done. I'd tackle one of the large blocks and then handle a couple of 'specials' as a palate cleanser, and then back to it.
But, again, the end result was functional, rather that spectacular - even for the 'specials'.
Oh, and once I was done I promised myself never again. Thus far, I've kept that promise the second time...
