Your best bet, given your experience, is to check around at local shooting ranges and see who in your area is turning out good, reliable, quality products in the type you are interested in learning about ( 1911 pistols, boltguns, AR's ).
Talk to a few people and see if the same name comes up a few times.
Make an appointment to talk to the gunsmith and see if he would be interested in taking on an apprentice to help around the shop. Explain your experience and skillset. There are A LOT of small chores that a small shop can use a good machinist to do the work for them and increase production, which is a great trade for you learning their trade.
These types of small shop situations will most likely be in your spare time and without pay, but you will learn a lot more than taking classes online or at a totally beginner "gunsmithing" school.
That is where I started and I learned a ton in a short time. Now I am more of a shop rat, because I needed a real day job. There is a guy in a very similar situation to yourself who works fulltime at the shop, part time pay, because of his machinist and shooting backgrounds, but the guy has learned enough to damn near be ready to take on his own work.
That is my best recommendation. You experience won't translate to entry level gunsmithing without boring you to tears and you will need some of the very basic skills to advance on to the more "real" gunsmithing.