How to remove pkgsrc orphan dependencies?

[Ottavio Caruso <ottavio2006-usenet2012%yahoo.com@localhost>]

My system has grown to be a mix-and-match of binary packages installed
with pkgin and other packages compiled natively from pkgsrc.

I have then removed some of the latter packages but I have Gbytes of
unused orphan packages.

I know that "pkgin autoremove" can remove orphan packages but that
doesn't take in consideration compiled packages.

I could force pkgin to "keep" some packages, but thay are really too many.

Is there a native way to achieve this goal?

How do you guys manage a system that grows a bit too big, without
sacrificing essential dependencies?

-- 
Ottavio