I mask off both sides and then use a gun all the way along with the
nozzle angle cut so the nozzle trails the gun. Then quickly run a wet
finger (washing up liquid mixed if you want) all the way along wiping
any major build up of excess silicone off onto a rag at the end of
each straight run (otherwise that crap gets everywhere!) Then strip
off the masking tape straight away. I leave at least a gap of 5mm each
side from the corner when applying the tape for decent adhesion or it
will just come away with a little flexing from the bath/work surface
etc.

Don't be tempted to keep touching up small imperfections cause you'll
only make it worse!