I use
http://www.ikea.com/au/en/catalog/products/80165855/ mainly because I bought a truckload of them some time ago. All I did was mark off 500ml and 1000ml and number each bottle (I use 1-20 on a 40l lowwines).
Re quantities...well, the 20%ABV cutoff is a good idea. After that, you are likely to be 'wasting your time/money/enjoyment factor for little return IMHO.
Personally, I haven't used a parrot during the spirit run (smearing etc) as the realtime 'smell' alone should give you an idea when its low ABV%, however your call, of course.
The acutal number of litres (in cuts) that you collect is very subjective and debated... and dependant on the ABV%/quality/quantity of the lowwines as well as the takeoff rate etc etc, I think. My guess was/is, If you expect to take cuts until its too much tails...then expect to take half of your lowwines and I reckon you'll be close(ish).....mind you, I've NFI really.
As an aside...a related question about jars/cuts etc is......once you have done a few spirit runs with cuts in such small quantities (aired and tested etc) AND you have got to know, typically, where the fractions are.....what size cuts can you reasonably take for future spirit runs (eg 1 litre, how about 5 litres when you are confident it is hearts :shock: , or what)????