So, I have a mage who's a fighter type, into melee, and I'm interested in him having a Mean Left Hook. Not for anything useful mechanically, it's just kind of nice to have him be able to punctuate a statement with a battlecry and a blow to the head.
The issue is, mechanically, training up his Brawl would take forever and is all around a horrible idea! What ways are there to raise his effective Brawl score without actually wasting two years learning how to fistfight?
Puissant/Affinity/Good characteristics?
A quality summa? I'm not totally sure but I think in this game you can read books to learn anything. Also a decent storyguide limits this to what makes sense
He could become a Criamon of the Path of Strife: they can use their Enigmatic Wisdom scores as a weapon score.
Alternatively, just have the troupe agree its a Virtue and buy it at character creation.
Puissant grants +2 to the Brawl ability
Several MuCo spells will raise his speed, toughness and strength.
But to be fair, he must train to be a good fighter. it is like saying that it takes forever to raise his Ignem to level 35 and so hoe he could raise it without spending seasons in the lab and library? Well, he can't. he must do that.
2 years practising brawl is quite a low time for someone that can expect to live to 100 years old easily. You can also invest your starting childhood points there and be done with it forever. It is rather easy to get 1 ability at level 4 for a starting character. With puissant and a few spells he will be quite a mean brawler. At least brawling mundane humans and animals.
Cheers,
Xavi
Since Brawl covers "dodging" it's not such a bad idea, depending on where you see it headed. If nothing short of double digits is acceptable, then, yeah, that time might be better spent.
But there is no way in canon to magically "gain Abilities" afaik. So, improving stats, that feed those abilities, or using magic to mimic the final effect is the best bet. (Or, with troupe approval, a house rule, natch.)
Rego Corpus, Self - aimed spell. The spell essentially throws his fist where he wants it to go with greater force - The Hammer.
An item, a glove perhaps. (Possibly his talisman???) Similar to the above. Possibly with a PeCo (or PeMe or ReMe for the knock-out blow?)
And, as Xavi says, there are endless MuCo spells that can increase stats or other aspects. Either permanent or long-term duration, he just keeps blowing in to his thumb until he's big enough, et voila.
Meanwhile some sort of wards to prevent counter-strikes, and he's rrrrready to rumble!
Salvete Sodales!
Becoming a great fistfighter without training seems to be beyond the limits of standard hermetic magic. One of the best things to do is to boost your relevant characteristics, but this means either rather high level Momentary ritual spells or even more high level normal spells if you don't want to spend vis on the permanent version.
But some hedge magicans can (within limitations) acchieve this. Just have a look at the SuccurroFortunam guidelines in the new Hedge Magic book. It is nearly certain that a hermetic mage has something to offer to those guys in exchange for their charms - of course using an amulet for an ettended period of time might lead to warping.
Vale,
Alexios ex Miscellanea
How about taking Flexible Formulaic Magic?
You'd still have to buy up your Brawling skill, but it'd be more valuable to the character since you'd be able to use increase the Penetration by reducing the range to touch.
Alternatively, maybe the SG would let you use the Non-Hermetic guidelines mentioned by Alexios to construct a Mythic Blood style virtue?
a nice ReMe or PeCo spell with range:touch and still spell could mean your punches have quite the impact. No one ever said that the touch for a range touch spell couldn't be a punch. Of course you would probably want quiet spell as well so no one knows you are casting.
To just be a great fighter without using magic, well, you have to train. (boosting dex, quick and str does increase your attack, init/defense, and damage respectively)
Amd if you can only boost 2, strength is less important than dexterity in the Ars combat system, due to the carryover rules of damage from attack. 
Cheers,
Xavi