First, your making a common error from people outside the industry and interchanging marketing and sales. They are really different roles. Decide the one you want to focus on initially.
And I really like you said "learn about marketing to support the work you do as a developer?". Sometimes dev side can be a bit elitist of their work vs marketing, but the devs that try to understand marketing side can add so much value. It can be as easy as knowing you can control a setting or function easily that itself can be a selling point that wasn't in the spec plan.
From a marketing side I dont know any boot camp, but I would say:
1) What you say about hire a professional is correct. Like anything you can read some books but there is always endless 'you dont know what you dont know' issues of inexperience that goes with any profession.
2) In the absence of experience, copy then do. Look into what companies known for good marketing do and within your budget/time limitations emulate that with your own flavour. I think this will often teach more than courses or books.
3) Understanding good comms are the foundation to any marketing campaign or brand. That's where it starts. For this I think books like 'Ogilvy on Advertising' give much more value than the typical 'how I growth hacked my company' type books. Get core comms right and your a long way towards selling a product, and it's much easier to fix up some web pages than redo a comms strategy. Also the biggest mistake I see people is trying to sell who they want to be, but you need to sell who you are. Find a truth and celebrate it. Sounds obvious but its one of the common mistakes.
4) Analytics, learn how to measure and monitor your sales and marketing. Knowing key metrics to monitor and check up on will be invaluable to your own activities, but also in getting the most out of others as you bring people or agencies onboard, and generally keeping people honest. With analytics 1) pick key metrics that you can influence. Too many people monitor points or with short timings that they cant respond to anyway, its just distraction then. 2) Pick down stream metrics as why your successful is less relevant than if you are. You can always work backwards when its deep review time and again too much funnel is a distraction. 3) Look at trends not numbers. It more important to know sales are steadily going up over time, than they hit a specific number. And likewise you want to know when things are tending down even if recent months are over target as you can fix the problem before they are under.
Overall Id say do stuff over take courses, I think the learning curve is much more effective that way as most marketing students use very little knowledge form a 3/4 years degree really, and probably learn more in their first 6 months on the job.
Good luck