three quick questions.
is it possible to merge 3 or more subtools into a new single mesh object?
so you can then use that model as a single subtool in another project.
also when you want to start poly painting and have different materials on each subtool what is the correct procidure.
also is there a quick way you can do a screen grab to show your progress?
Yes you can merge subtools together.
You need the Subtool Master Plugin.
You can get it here:
http://www.zbrushcentral.com/zbc/showthread.php?t=57154
and regarding your question with the different materials
Here´s a great tutorial:
http://www.zbrush.info/docs/index.php/Materials_and_SubTools
regarding the screengrab. Do you mean if you can record your progress?
If so:
http://www.zbrush.info/docs/index.php/Movie_Palette
Hope that helps
Happy Zbrushing! 
the quickest way of getting a screengrab would be to save your document as a PSD, BMP or jpeg i guess.
head over to:
Document and klick export and you be able to save the current frame or what you want to call it as a standard image.
i hope that was the answer you were looking for!
Sorry! Wasn´t sure what you mean with “screengrab”.
The link I gave you is for making a movie.
Moni-Poroni: thank you so much …sub-tool master is super sweet …this is exactley what i was looking for! awsome
thanks for the other links also so kind…!!
making somthing new:D