kackieanne

No such thing.
I think using a surgical marker is a viable option.  They are sterile and single use.

I saw a Blood Hound prototype 5-10 years ago.  I wish the FDA would work faster.  I think the technology looks very very hopeful. 

An EXCELLENT question Darren ! I look forward to some interesting debate.

NO!
I am a professional blood group sereologist!

My students really find the simulated diffs on this website to be extremely helpful.  A subscription costs $35, and you can choose regular diffs or advanced diffs.  The website is 
https://www.labce.com/ and you want the "WBC Differential Simulator".  As to distinguishing reactive lymphs from monos:  there are lots of ways to describe the differences, but in the end, it just takes seeing lots and lots of cells.  Eventually your mind will make neural networks and you will just recognize the cells.  To me it's like the experience of signing up for a class with people you don't know.  At first, you have to make an effort to remember names and recognize faces.  You might get two classmates confused.  You might have to memorize distinctive characteristics:  glasses, hair color, etc.  Eventually, though, you just recognize them--even if they change hair color, or wear contacts one day.  Your mind is designed to learn to recognize things by their appearance, so relax and give your mind as much experience with seeing these cells as you can possibly manage to give it.    Keep looking at cells even if you are sick of it.  You will eventually learn.  Also, everyone learns at a different pace, so be patient with yourself and stick to it.  Lab CE will help--I'm sure of it!

WBC Differential /Band cell counts:
Suggest review these publications:
CAP survey 1995 Lab Hematol 1,89 - Inter and Intra observer consistency
Eur J Haematol 2006:76: 251-254. Good article Re variation of WBC Diff with a number of morphologist review digital images
ISLH recent publication June 2015: ICSH recommendations for the standardization of nomenclature and grading of peripheral blood cell morphological features - which recommends that band cells be counted with neutrophils (Also directs to an image library)
I would question the value of this enumeration in the 21st cent., also consider the significant variation (LoU) of band cell counting..
Our local evaluation with digital images, gave a LoU of > 40% (Which is a good result!), hence we do not report bands cell counts, but will only make a comment.