If you have a unit you need resupplied ASAP, put multiple supply sources next to it:
All supply units, regardless of cost, spread supply at the same speed. From the perspective of a single tank, it doesn’t matter how many other tanks are being repaired by the same truck – its repair speed won’t decrease. Importantly however, it can speed up: there’s no cap to how fast a unit can receive supply, and each supply source transfers supply separately, so parking multiple cheap trucks next to your superheavy will repair it much faster than using a single HEMMT or Mi-26.
This is usually just an argument to use cheap trucks instead of expensive ones, but the Longbow is particularly affected because of its long reload. Putting a few 10pt trucks next to the FOB will dramatically shorten the time spent procuring more hellfires, allowing you to maybe even deploy the same Longbow twice in a match.