I used this software for all my reduction of data obtained from APO
and IRTF.  The options are listed below.  dt represents the known
deviation in exposure time with GRIM.

1) Make a flat image
2) Make a dark image
3) Shift image
4) Display an image
5) Reduce image
6) Aperture photometry
7) Subtract two images
8) Flat field an image
9) Interpolate between two images
10) Remove bad pixels
11) Remove cosmic rays
12) Find centroid
13) Coadd images
14) Correct for nonlinearity of GRIM chip
15) Curval
16) Remove box
17) Clear screen
18) Change dt (currently -0.185)

Note, this uses the IDL Astronomy Users Library (available at
http://idlastro.gsfc.nasa.gov.  This requires you add astrolib/pro to
the IDL_PATH environment variable.