You might look at a binocular disecting scope. I never used one to look at flint but I did a lot of work with biology specimens. You can get most any flint artifact under one.
A loop or similar hand held of 10 to max 30 X is very worthwhile to quickly scan for areas of further interest.
Radio Shack sells an illuminated variable microscope of 60 to 100X ( $12. cat# 63-1313 )that will positively enhance an edge for the detail you are looking for. I've used their old 30 to 70 variable for years on fossils.
"testing" a new microscope can be very interesting too, like on an ink line on paper or human skin ( on a dirty callous encrusted digging hand ! )