for a quick loud master, without the need to delve into compression, I would suggest running 2 mastering limiters in series. Neither should push more than 2db of gain reduction.

Limiters to use in order of quality and transparency.

Voxengo Soniformer (not for beginners, very very hard to use initially)
Voxengo Elephant.
Sonic Timeworks Mastering Compressor
Crysonic Spectra'Phy
T-Racks Clipper (only the clipper, the rest is junk)
Sonnox Oxford Limiter
Waves L3