In addition to s2art's suggestions, which should work fine, you can also use a percentage transparent fill with a white pen. This will "grey" areas down a little, although you may need to try different fills to get the effect you want. Another possibility is to stack two (or more) copies in layout. The bottom one would be totally grey and perhaps a narrow line version. (Use a different pen set.) The top elevation would have just the foreground areas shown, and would be the heavier lines. Personally, I like the marked distant area solution the best, since it's automatic.
Richard
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Richard Morrison, Architect-Interior Designer
AC26 (since AC6.0), Win10