Hi. It sounds like the damp towel the former owner used, may have had fabric conditioner used as well as washing powder. I am very sensitive to the perfume smells in fabric conditioner, so I think it could be that that smells strong. Very unpleasant for poor little hammy. But - you are right - hamsters can have sand baths and if he rolls in the sand it may help the scent dissipate quite a bit, gradually. It will wear off, but keep an eye on him and see that he seems ok in himself. He will be a little bit stressed at the change of house, owner and cage anyway and usually it's recommended to leave them in the cage to settle in for 2 or 3 days without being disturbed, so they can familiarise themselves with the cage and scent mark to find their way around.
His normal behaviours may be a bit different unless his scent marking is stronger than the smell on his fur. But he might pee all over everything to try and get the scent back to normal. If he does, don't clean out just yet - better the cage is a bit whiffy for a week or so and he recovers from his perfume bath
You can't use just any sand for a sand bath, it needs to be Chinchilla bathing sand (not dust). This one is commonly used
https://www.amazon.co.uk/Supreme-Pet...a+bathing+sand
It might not be available locally although some larger pet stores might sell it. Amazon and Viovet sell it but it could take 2 or 3 days to arrive unless you have next day delivery. And Amazon only do it as an add-on item for next day delivery. I tend to buy two from Viovet so I only pay one lot of postage. You need to sign up with Viovet though. Then there are delivery options - either first class or next day delivery I think - so it could take a day or two then.
I think meanwhile just make sure he has masses of substrate/bedding and nesting material so he can roll around in it, or pee in his nest to get his own scent back (which he might do). Plain white toilet paper is the safest nesting material and they like it. I take a few sheets and tear them into 5 or 6 sheets lengthways and put a very large mound of it somewhere in the cage so he can pouch some and take it to his house to build a nest.
Apologies if you already know all this
Substrate is the stuff for the floor of the cage - the deeper you can put it the better as then he can burrow down in it. 3 or 4 inches minimum is usually recommended but I try and put at least 6 inches in (ie fill the cage base to the top and mound it right up in the centre where it won't fall out of the bars).
He may well groom himself but if he doesn't like the taste he may find a way to get rid of it by drinking more possibly.
So just do what you can and keep an eye on him
And get some chinchilla bathing sand and put it in the cage as soon as you can. Something like an old ice cream tub or a pyrex casserole dish can make a good sand bath and push it down into the substrate a bit so he can get in and out easily.
I also used to use a litter tray for our Syrian and put the same sand in that and he would often roll in that a bit too. He would pee in the very back corner and then sit in the front part to groom or roll in it a bit. I used this open plastic corner one which was a good size for a Syrian.
https://www.amazon.co.uk/d/Houses-Ha...=Hamster+Potty
Do you have a Pets at Home nearby? They seem to sell the Chinchilla bathing sand.