In article .com,
says...
Some grafitti has been spayed on a nearby wall overnight and I'd like
to hasten its removal.

It's constructed of "blue brick" which it fairly smooth and I'm told is
extremely hard.

I believe that a problem with applying paint stripper to brickwork is
that it can be absorbed (together with the paint) into the bricks and
makes matters worse.

Is blue brick porous in this way or can I apply whatever I like with
confidence?

This happened a couple of years ago and it took about 6 months for the
grafitti to disppear through natural weathering.

It's actually a railway wall and so not strictly my responsability
though it does reflect badly on my property. The road is faily busy and
I don't really want the humiliation of scrubbing away at it for ages
while watched by passers by. So if there is something I can slap on or
spay on in a couple of minutes that would be great. I don't expect
instant removal, but something that would get rid of it in weeks
instead of months would be a great help.

Any suggestions?

Blowlamp?