Pre-washing is one of the most crucial stages if you want to achieve a near touchless wash, especially during winter months. You need to get as much muck and dirt of the car before you get to it with you wash mitt.
Power Maxed wash & wax or their TFR are fantastic products. Check the reviews out on Detailing World.
If you want a decent snowfoam there are loads out there to choose from , I use Autosmart Ultramousse goes on like shaving foam
Autosmart Active XLS is also very good , has a little more bite.
Get yourself a snowfoam lance too (about £45)
If you do not want 5 litres then go to fleabay and use either Autorocket or Mallissoullution, both good sellers
Enjoy!!