0402 packages - absolutely tiny. I'm wondering if it's possible to reflow solder them using a hotplate/skillet or toaster oven. Does anyone have any experience with doing this?
There's nothing wrong with hand-soldering 0402 or even 0201 with practice. 0402 I can do without an inspection microscope, but 0201 is getting too small to do without one. Then again, I also solder 0.5mm TSSOP and TQFP packages without a magnifier or microscope. Just need to take your time, use flux and relax.
I have no expirience in manual dispense, but I know the automatic and semiautomatic paste printing. Talking of how much manual effort is involved, consider this. When you are using oven for reflow step, then there are no hands involved. So the limit is defined only by 2 factors. Proper amount and type of solder and thermal profile.
Component placement is not critical, because reflow is automatically aligning components with wet forces. The geometry of footprints and solder masks is not manual either, just follow the specified footprint for each component. Thermal profile is easy to achieve with measurement, timing etc. For simple components (not a bga or 100 pin) the geometry of paste is not critical.
So limit is in accuracy of amount of paste dispensed on a pad. For manual dispense, I'd recommend create a syringe with some screw pusher and calibrate the amount of paste per angle of screw rotation. This must work for any sizes.