I’m wrapping mine in this and it works great.
Wrapping Heating Pad for Pain Relief, Comfytemp 7"x 14" Mini Electric Heating Pad with Strap, 9 Heat Settings, 5 Auto-Off, Stay On, Moist Heated Thera https://www.amazon.com/dp/B08DV46XQ5/ref=cm_sw_r_cp_apip_tQaChLCBPoAI8
If you want to get serous about cleaning the interior, I would suggest looking for a stemware sponge or brush, like is used to clean wine glasses and champagnes flutes. Very similar to a brush for washing baby bottles, but typically slimmer and is available in softer sponge-like material that is not as abrasive.
HERE is an example of what I am talking about. I should add that I do not own one of these, but it is something that I have thought about, and this is the best tool that I have found for the job. I suggest you do your own research before you buy one of these to make sure it will work for you and will fit inside your sleeves.
Using THIS Heating Pad that I bought off Amazon. It is 12” x 24”, so it’s large enough to roll or wrap around one or two sleeves AND a bottle of lube. Mine stays plugged in next to the bed, so it’s ready to go at any time. I can run in, pick my sleeve(s) for the night, wrap the sleeve(s) and lube in the heating pad, and set it and forget it. I’ll usually tuck it under the pillow so that it’s within arms reach when the time is right. The sleeves are much easier to roll if they a warmed through prior to rolling. I can reach over and grab it from under the pillow, get it rolled and ready while other activities are in progress, and slip it on within a few seconds. I’ve found that the heating pad is less hassle than water because it maintains constant temperature and I like the inside of my sleeves to be completely dry. I realize I could use plastic bags with water, but maintaining the temperature and the hassle of having water in the bedroom is just too much for me. With the heating pad, you can leave it for 20 minutes or two hours and it will still be warm. A warm sleeve, warm lube, and a warm partner make for a much more realistic experience.
I bought this electric heating pad from Amazon specifically for warming my sleeves and lube. At 24” long, it is large enough to wrap/roll around two sleeves and a bottle of lube. I keep the heating pad plugged in next to the bed. I usually pick my sleeve(s) for the night, wrap it/them and a bottle of lube in the heating pad, and tuck it under my pillow to warm. It takes maybe 20 minutes to warm to my desired temperature, but I frequently leave it for an hour or longer while we “warm up”. The medium or low setting is probably best, but I like to use high. The High setting gets it a little too hot, but it works out that it cools down perfectly during the time that I am rolling it an anticipating putting it on.
For lube, my vote is for Bad Dragon Cum Lube. We’ve only used the white, so I don’t have an opinion about the clear, but reviews say that they’re both very similar. We had never used either Bad Dragon or Sliquid until I bought my first Blissfull Creations sleeve, at which time I bought a bottle of each. We tried the Sliquid several times first, before trying the Bad Dragon, but we were not satisfied with it. In my opinion, the Sliquid does not feel as “slick” as the Bad Dragon. Also, I feel that the Sliquid dries faster than the Bad Dragon, and has to be reapplied more frequently. To-date, I have only used 1/4 of the bottle of Sliquid, but I am on my third bottle of Bad Dragon.
As for warming, I have tried both using hot water and using an electric heating pad. My vote is for the heating pad. I purchased this one from Amazon specifically for the purpose of warming my sleeves and lube. At 24” long, it is long enough to fold over or roll up with two sleeves and a bottle of lube inside. I can pick my sleeve for the night, wrap it and a bottle of lube in the heating pad, and put it under a pillow or on the bedside table. Water was more hassle than I prefer. With the heating pad, I can “set it and forget it”.
So I was able to go back into my amazon purchase history. This toy I bought a while back isn't large in the sense of length, but it is girthy at what seems to be 2.5" in circumference.
https://www.amazon.com/gp/product/B010RBS8NW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I'll say this, she didn't dislike the toy, but I had a smaller bullet vibrator that she enjoyed clitoral stimulation with more. That being said, we were also very new to the whole thing and I didn't use lube etc, thinking she was wet enough. Now that I look back, and talk to people such as yourself, lube is everything it seems. This also seemed to be a crappy chinese knock off of name brand. We've been together much longer now and are much more comfortable talking about what we want in the bedroom, so I think she'd be open to it.