Firstly, what colour is your Cali? In my experience darker colours need much more work to keep them looking at there best, especially if you live in a hard water area. If it's Black then it could look pristine when finished if you've used the right technique but then only for a nano second.
Never wash your van on a hot sunny day otherwise it will end up being a struggle and it won't look great when finished as the suds will dry on the paintwork before you can rinse them off. If it's black it is a nightmare. The best conditions for washing are wet rainy days but at the very least overcast and cool weather. You need the body to stay wet preferably with pure rain water and not tap water containing calcium deposits etc.
I personally use the two bucket method which works very well for me. Get yourself two large buckets with a raised grid at the bottom of each. They sell them on Ebay. Thoroughly jet wash the van first to remove all surface grit and grime etc. Use a wide spray, never a concentrated jet, and don't go closer than half a meter from the van. Make sure you thoroughly do under the wheel arches as well. Use one bucket to wash and when the sponge or wash mitt needs re-wetting rinse in the second bucket containing clean water. Then re-soak the sponge in the wash bucket. Any dirt and grit on the sponge or wash mitt should end up in the bottom of the rinse bucket beneath the grid and out of harms way. Use a good make of car washing product. Never use washing up liquid.
Start with the roof. You will need a stable step ladder but better still a step platform to work on. Don't try and over reach as it could end in tears. It's best to use one of those long handled soft car washing brushes on the roof as getting to the middle can be a bit of a stretch. Once washed thoroughly, jet wash off.
Then do the upper part of the body work and windows down to the waste line. Use a sponge or wash mitt only for this and the rest of the body work. Then wash that off thoughly. Be carefull not to direct the jet washer at the gaps around the sliding windows for any length of time or you could have water ingress.
Then wash the lower portion of the bodywork making sure that you regularly rinse out the sponge and re-soak in the washing water. This lower portion of the body work usually gets very dirty and needs that extra bit of cleaning. At this point you can open the doors and wash the door jams and sills with the sponge. Then close the doors and jet wash the whole lot off. Direct the jet washer to the door shut gaps to wash out of the suds from the door shuts.
Finally wash the wheels and tyres. It's best to have a stool for this as it takes a while to do them properly. I use three different sized wheel wands which are like fluffy sausages on sticks. Again you can get them on Ebay or from an automotive cleaning suppliers. First jet wash the wheels to geat the worst off then use the remaining soapy solution to thoroughly clean the wheels on the outer face and on the inner face with the wands. I also have an Autoglym wheel brush which is very useful for cleaning in the difficult crevices like round the wheel nuts and tyre valve. You could use a paint brush but I would wrap the metal collar with gaffer tape or it might cause scratches. Never use corrosive wheel cleaners as they will escalate corrosion if the wheel is damaged in anyway. Finally jet wash off.
If it is still raining when you have finished washing then it's job done. If not then use clean micro fibre cloths to towel it dry. This is a must if you have a black van as every mark will show. These clothes are very cheap to buy, very effective and much better than the traditional wash leather. I suggest keeping a stack of them purely for drying the van. They come in various colours and I would suggest using specific colours for specific jobs, i.e Blue for cleaning windows and green for drying the paintwork. Use a different colour for applying and removing polish. Washing them never fully removes the residue of the polish and you don't want that on your windscreen.
I usually give our van a good thorough coating of quality car wax twice a year, once in the spring and again in the autumn after first having given it a thorough wash and dry. Include the alloy wheels as it offers them some protection as well.
Finally, as we live in the country our van gets properly plastered in muck of all kinds on a regular basis especially during the winter months. I don't wash the van in this manner every week but instead do it thoroughly on roughly a monthly basis. However, I take the vehicle to the local jet wash every week and blast of the muck and grime from every where but especially the brake dust from the wheels and salt from underneath and bodywork. I only use the cold jet wash function. IMO, never use the wash brush at these establishments as they get used on all sorts of vehicles from builders pick up trucks to mud plastered off roaders. You can't be sure that they won't scratch your paintwork.