Hi,
Riding defensively is simply not riding aggressively. Take lines car would take in moving
road position. to overtake parked cars rather than swinging out near the car. Signal your
intentions clearly. e.g. anyone who indicates right to overtake a parked car is clearly a
muppet,* you indicate right when you really need to go right and get to the road centre.
Good road tyres on a MTB will make a huge difference to the ease of a commute.
http://www.chainreactioncycles.com/michelin-wild-run-r-mtb-tyre/rp-prod48134
Chalk and cheese compared to typical MTB tyres. And FWIW on tarmac they
will have outstanding wet grip, bike tyres on roads simply don't need tread.
Also fit mudguards, carry a spare tube, and the bits to change a tube.
rgds, sreten.
* Drivers clearly don't expect you not to overtake parked cars and don't
appreciate much a a meaningless signal, a far better signal is your
moving road position, which should be slow and deliberate.