We cleared our own freight at Salwa and had no problems.
Our rep wasn't there and a Qatari who seemed to be hanging about offered us a cup of tea. We accepted and he turned out to be Director of the customs post. Drivers were bringing in samples to clear their loads and he gave our kids a packet of crisps each from the samples.
They automaticall handed them round. After that we could do no wrong, the freight was cleared within 10 mins and was delivered within the hour to our house. The driver (a Brit) couldn't believe it as it normally took 4 days to clear.