Hi Darren,
Yes, just to clarify, base coat would be panzer grey followed by the appropriate "desert yellow". Depending how weathered and beaten you want the tank to look, then some of the grey would show through, like edges and scuffed surfaces made by the crew.
Rick brought up the question of using Tamiya's desert yellow. Well, it is much more accurate than using their dark yellow. I haven't tried it myself, but do recall other people suggesting it. In an earlier post I introduced a list of paint manufactures - they all attempted to match their colours to paint chips of the RAL series.
When I get a chance during daylight hours, I'll post a digital shot so Tamiya's desert yellow can be compared to Braun RAL 8020 - the colour specified for use on March 25, 1942 and for the duration of the African campaign.
For now an image search produced these swatches:
Tamiya desert yellow
RAL 8020
Jack