Okay, you've decided that the ski season is definitely done now. It's been 2 weeks since the last crust cruising, and there's no snow in the forecast. It's time for some spring cleaning...
If your skis don’t have wax on them – skate skis for instance - give them a good brushing, tip-to-tail with a copper brush or other soft metal brush. The purpose of this brushing is to clean out the base structure, removing the old wax and loose dirt.
If your classic skis still have kick wax on them, remove it. I use a plastic putty knife and then Toko Gel Clean wax remover for this. Scrub a bit with a paper towel and a bit more wax remover, and wipe them clean and dry. While you've got wax remover and paper towels handy, why not clean the sidewalls and tops of the skis?
Now “hot scrape” the bases: rub a layer of a soft paraffin wax down the entire length of the ski (yes, on classic skis, too). Now drip a lot more on – I usually run a continuous stripe down both sides of the groove. Iron quickly about three passes. While the wax is still molten, or at least soft, scrape the wax off with a sharp plexi scraper. Let the skis cool completely, then brush thoroughly with a stiff nylon brush.
The hot-scrape process lifts dirt and pulls old wax residue from the ski, into the hot molten wax, and the scraping will remove it. The brushing then helps clean out the structure. After the hot scrape, drip on and wax in (a couple passes will do) some of the same soft wax over the whole length of the ski, including the kick zone. The skis are clean, protected, and ready for summer storage. You might put a piece of tape on the skis and write which wax you used; it saves confusion next November.
Skis that have been stored clean and with a good coat of wax will be ready to go when the snow falls next winter.
If your skis have some damage or they are old “rock skis”, you might think about sending them in now for stone grinding. Often a pair of “rock skis” can be transformed into race quality skis (or “rock and roll skis”). If nothing else you’ll have good training skis for the early season.
If you left your klister-covered classic skis in the bag for the past few weeks, and have discovered a mess, then cleaning your ski bag is another job; I suggest some kind of alcohol solution, chilled, to help with that process.