Why not post all the positions in one ad in Aviso?  I would respond to an ad
found in that publication if it included a number to call for more
information regarding salary etc. (although that might be more trouble for
you to receive so many calls).  Also then you may weed out people who don't
have experience with museums.

the address for Aviso is:
AAM Aviso Ads
1225 Eye St, Ste 200
Washington, DC 20005
202/289-9122
fax 202/789-1355

Good luck