Brian -- who worked as Drake's dialogue coach on "Drake & Josh" in the early '00s, and who's worked on countless children's shows through the years -- surfaced this week in L.A. as he tried covering up from the rain, using a blue puffer jacket while exiting a vehicle.

The showbiz veteran kept the jacket over his head as he made his way inside his home. Looks like he wanted to make it inside pretty quickly -- as he carried his keys in his mouth and darted into the house.

This would mark the first sighting of the guy since Drake revealed he'll tell his story on the ID doc 'Quiet on Set' ... in which he's expected to claim he was a victim in Peck's criminal case from 2004, when he was convicted of performing a lewd act with a 14 or 15-year-old and oral copulation with a minor under 16.

Unclear if Drake will allege both of these counts pertained to him ... or if someone else was in the mix. In any case -- this will be the first time Drake has spoken about this publicly.

Brian was sentenced to 16 months in prison and had to register as a sex offender. He's continued to work in Hollywood since that whole ordeal ... with a crap ton of credits under his name post-2004, including recognizable shows and movies.

Drake isn't the only former child star to speak out against Brian ... "Boy Meets World" alum Maitland Ward even told TMZ in February that she was always suspicious of him when he worked on her show, which also starred Rider Strong and Will Friedle.

Rider and Will acknowledged their relationship with Brian was odd -- sharing that they previously came to his defense because they believed his story about falling victim to "jail bait." Worth noting, they never alleged he'd done anything inappropriate with them.