Materials and application are very important not only to the artist's statement but to the longevity of the piece. With new paint mediums being developed weekly, artists need to be informed about their chemistry. Oooo, combining art and science... (artists today know how economical it can be to have a conservator on speed dial). However, a basic knowledge of historical application can be applied to todays materials, "thick over thin" when using oils, "water is heavier than oil" when blending oils and acrylic, and "graphite can't be washed away". The chemical, molecular reasoning behind these traits is, frankly, unnecessary in order to understand the point. These have all been tested by past artists and found to be true. Since we are faced with new materials every few weeks, artists are finding the inundation of new "stuff" too appealing to not use and older methods are just that, old. But as a chemist, "newness" of the material doesn't change the principles which are still the same and still apply. You can't beat chemistry.
When the work is complete and it's time for the final coat of varnish, the question returns, "Am I doing this right?". When it comes to acrylic or any other poly based medium (read labels), the work is already sealed to environmental conditions since it's already made of a plastic derivative. So that leaves oils. As many oil painters know, oil takes a long time to dry; rule of thumb dictates a year before varnishing. There are, however, synthetic varnishes that can be applied throughout the drying process that maintain the visual experience but will not interfere with the oils' drying. Soluvar is good go to, it's easily mixed to the consistency needed and easily sprayed for a final varnish.