Hello Muscleman, I am gonna start doing what you are doing this year. I already purchased a car this winter but it's pretty much impossible for me to work on cars during the winter where I live because I do not own a garage.
Ok, so here are the important things:
For interior, you want to vacuum every nook and crany then wipe down everything (including headliner, fabric surfaces and all).
Then work on problem areas if there are any. I would do a carpet and seat shampoo. If you don't have a hot water extractor, there are 2 cheap ways to do this: Purchase a Bisell Little Green machine (or their car specific equivalent) for about 100$ or use a wet or dry vacuum cleaner. If you have neither, I would go with a Rigid wet and dry vacuum cleaner because it will be dual purpose for you. If you already own a vacuum cleaner then I would buy the Bisell LGM for use of cleaning.
For interior protection, hyper dressing works well. I would dilute to natural look level but that is a personnal choice.
Exterior: If you have the tool to do a one step polish, I would do that. I like Meg's Reconditionning creme but any polish will most likelly be a good improvement. What I like about RC is that it's a polish and sealant in one, so you save a step.
For tires, a good APC or better yet degreaser if you have one. Good cleaning of the rims as well. Then dress the tires and Wheel wells. I use a water based product, don't like any of the silicone stuff but if that's all you have it's still better than not putting anything on.
Make sure Windows are really clean. There are several car Windows cleaning techniques available on Youtube. Clean Windows are a combination of using the right Tools, products and techniques. But as a rule of thumb: use a Windows specific microfiber tower to dry the Windows and always clean the Windows twice.
You should also learn how to do an engine bay detail, in my book a clean engine makes a big difference when buying a car.
Hope this helps
