Galina
Don't try to "cover" the shallots with salt. I usually start with three handfuls and during the evening check the "pile" so see if the salt has disappeared. if it has I add more. There should be a bit of salty liquid in the bottom. When I wash the salt off I don't plunge them into water but do it in a sieve under the tap. I then dry them off again.
I always wash the jars and dry them upside down in an oven with the temp about 100. whilst the jars are drying I put vinegar, a few mustard seeds, black peppercorns in a sauce pan and warm but not simmer. You should be able to put a spoon in the liquid and still hold the bowl without burning/hurting your fingers! The vinegar is up to you but sherry vinegar or red wine vinegar is special. If you buy pickling vinegar just warm it without the spices.
I then put the shallots into the jars, I usually add two garlic cloves (skinned and the bottom cut off, still whole though) and one or two small dried chilli's. This depends on whether you like the shallots "hotish". When I have squeezed in enough I pour in the vinegar and try to get the seeds and peppercorns in as well. when the shallots are covered seal the jars and store in a cool dark locked cupboard. I try to turn the jars over at least twice before cracking them open. Leave until Christmas eve and enjoy.
There is one big problem if you do it right, none left after new year and you do not have enough ground put by to grow more that year. Friends and family love you if they get a jar and ask to be put on the "pickled shallot" list for the next time.
Once you have tried them you will never go back to pickled onions.
Pickle and be damned
Bill