I have always found Independence (was Yellow Tools, is now Magix) to be and easy and intuitive way of mapping samples and creating instruments. Mapping samples across the keyboard and creating velocity layers is graphical and straight forward.
It's not nearly as versatile as Kontakt, but simpler to use in this application (IMHO). Unlike Kontakt where you have to get the full package there are a number of options depending on the amount of factory content you require.
You could try Independence Free
http://pro.magix.com/en/independence/independence-free.1013.html which can work with up to 25 wave files. That may or may not be too resstrictive for your purposes, but it is a good demo none the less with 2GB of useful content.
There are
other versions without the restrictions. The difference between Basic and Pro is in the sound library files provided. The factory sounds are a bit long in the tooth but still very good. The Candy Saxophones, Majestic Basses and Symphony Orchestra (which is a "lite" version of Kirk Hunter high end orchestral libraries) are particularly good. But if you have no interest in the factory sounds you can just get the software suite for 49 euros (+ tax depending on your location.)