If done right, you will rarely be blowing off components - and even if you do then you just replace them.
Yes -- In really challenging situations, you can protect surrounding parts and keep the hot air where you want it by walling off the part to be replaced, either with a protector like
this, or just use some wide kapton to create walls where needed. This is also a good way to protect things like plastic connectors from damage. Temporary solder mask (
example) can work well for holding small passives in place that are too close to wall off.
Hot air always benefits from a good sticky paste flux, you want something that really stays in place. For installing new parts via hot air, a little dab of flux on the bottom of the part can help, since it brings fresh flux right into the joint as the part is placed on the preheated footprint.