If you think an individual track sounds too muddy or not bright enough, first CUT AWAY in the mids and low-mids before adding highs.
Make sure you CUT AWAY the lows in every track that does not need it. To find out, set a High-Pass-Filter ("HPF") to 40 Hz on every track and move the frequency up, until you hear it working. Then stop.
If you still feel the need to boost highs, first find some spiky frequencies in the highs by taking one EQ band, make the Q very sharp, boost it by 10 dB and sweep through the upper frequencies (from 1K up to 20K) and find very resonant or spikey frequencies. If you found one, turn leave the Q sharp and turn it down like 5 dB. After that you'll find that you can boost highs better, because you're not boosting that frequency so much as well.
To get a sweeter high-end boost, set the high band of your EQ from a shelf-type to a shallow bell type (Q around 0.3).
Like Clark Kent said, stay away from master bus EQing, but EQ the individual tracks.
Do not EQ the tracks in SOLO mode. Always EQ with all track running.