Try this: put the Steinberg Brickwall Limiter (threshold @ -0,3 db, release fully counterclockwise, auto off) in insert slot 7 or 8 of your master channel. Raise the master channels gain (pre section) until you have a comparable level to commercial masters.
That way you get it loud. Don’t wonder if it doesn’t instantly sound like a commercial master, but it will get as loud as you wish. Refine the sound by using primarily EQs and compressors in the upper slots of the master channel.
To get a really great result, your mix will have to be really good in the first place. Smashing it against a brickwall + pumping it up ruthlessly will reveal any shortcomings in regard of how the mix works at your intented level. Re-tweak the mix if needed.
There’s much more to ‘real’ mastering but you’ll get somewhere for sure.