For heating, unless you have extreme heatsinking issues through the board, a simple wand type hot air
skillfully applied can do a lot. For prototypes I don't use an oven, nor do I want to scorch boards on a hot plate - I just do it with the wand while watching under the microscope for any issues so that I can immediately correct them.
Various preheat from below solutions may make sense as well.
That's all fine for QFNs and anything with perimeter pins. The bigger problem with BGAs is placement. At course pitch you maybe be able to do it visually in reference to board features you trust, especially if you have something like an auxiliary microscope webcam you could aim in from the sides to double check. But the proper tool is one which has dual imagers or a prism, so that you are looking "up" at the chip on a vacum pickup slide and "down" at the pads on the board and aligning the two superimposed images. When satisfied you move the imager out from in between the two and lower the head with the chip down to the board.
Here's Louis Rossmann doing it manually:
https://youtu.be/4Y2y6zpupd4?t=30m41shere he is (coaching someone) to do it with a basic implementation of a proper superimposed image BGA placement machine:
https://youtu.be/Shn7LdIrViQ?t=2m55sAll that said, one of the biggest problems to hand-build boards isn't technical, but just the time and tedium of pulling out all the little parts and placing them one by one in the stenciled paste. It's not the chips, it's the passives. Definitely get a vacum pickup, after discovering the Aoyue was absurdly oversized the next time around I converted an aquarium pump.