I have only taken a look at the 2009 NFL Combines for this question.  It would be a good strategy for the Skins to aggressively target the UDFA at least for some positions.  It takes some vision to see what is coming in 2010.  Apparently the Panthers used this tactic in 2009 (see below).

2009 Combine running backs 40 yd times for undrafted free agent running backs.
Name                          Time Team     Status   Grade
Johnson, Ian               4.46 Minn       Dev          36
Sheets, Kory               4.47 Miami      Act           57
Brown, Donald            4.51 Ind          Act          89
Goodson, Mike            4.54 Carolina  Act          70
Kimble, Anthony          4.68 Jets        cut          30
Ore, Branden              4.69                Nip         30
Southerland, Brannan 4.69  Jets       Nip          42   (full back, 6’, 240lbs)
Johnson, Jeremiah      4.71 Texans   RES        59
Sutton, Tyrell              4.75 Carolina  Act          31
Nip = not in NFL players list

Scouts Inc. GRADE KEY
90-100 Rare Prospect, 80-89 Outstanding Prospect, 70-79 Solid Prospect, 60-69 Good Prospect, 50-59 Adequate Prospect, 21-49     Borderline Draft Prospect, 20 Free Agent Prospect, and 10 Not a legitimate Prospect.

This sort of review can be expanded for other positions, but the Skins would need to be ready to jump on it.  These prospects are not exactly hidden before draft day three.