To use the characters in the standard Wingdings font (which should be resident on most modern LaserJet printers), you ideally need to use the full font selection sequence; for example, to select the font with a pointsize of 15 points, use:
<Esc>(579L<Esc>(s1p15v0s0b31402T
where <Esc> represents the escape character (the character with decimal code 27, or hexadecimal1B).
As regards the USPS Intelligent Mail Barcode: none of the modern LaserJet printers include a relevant font within their printer-resident sets, so you'll have to obtain a suitable font (either within an add-on hardware DIMM or cartridge suited to the printer, or as a PCL format soft font), in which case the documentation from the font vendor should explain what font selection sequence is required.
