*Hi there, * I'm looking for any good gender benders.
For example, the guy mostly dresses up like a girl. But the demographic is **shoujo. **

you request is rather vague I don't know what is "good" that you mean , in this case you should seek in "Gender Bender" or even advance search

https://www.mangaupdates.com/series.html?act=genresearch

Or else you should make your description more details . That will narrow the search

anyway for guy dress like girl or guy become girl
Americano-Exodus
Ame Nochi Hare (Bikke)
Muyong Jiyong
He Is a High-school Girl
Nicoichi
W Juliet

Have fun

Forgive my poor english

Here are two I can think of right now:

Tenshi ja nai!!
Oiran Girl

To find more, you could try an advanced search (like hi2moony said) with the category tag "Androgynous male lead" and include gender bender and shoujo as the genres.

"The great man is he who in the midst of the crowd keeps with perfect sweetness the independence of solitude." - from Self-Reliance by Ralph Waldo Emerson

Kyou Kara Yonshimai
Mint no Bokura
Kimi no Neiro
Ai no Shintairiku
Henshin Dekinai
Kakumei no Hi

Others, perhaps not exactly "shoujo" but not bad,

Aoi Hana {josei}
Hourou Musuko {seinen}
Bokura no Hentai
Yagate Kimi ni Naru (ongoing)
Girl Friends (by Morinaga Milk)
Shitsuji Shoujo to Ojou-sama
Prunus Girl
Angel Sanctuary (worth a try if you like philosophical, religious and sociological stuff too)
Half and Half
Hana wa Nisemono (if you can take somewhat sketchy art)
Kashimashi

Also, usually, Gender Benders aren't often "shoujo" if you put the overly smutty yaoi titles aside and the like aside from my experience. Usually I find them classified under "seinen". Maybe in Japan the seinen demographic likes this? Who knows. Best to search for what you like yourself by filtering through them personally though. I just gave a list of what I've come across. I thought some were bad, so I didn't list those, since I'm already doubtful about some of these but you could give it a try. You'll never know unless you try after all.

"Nationalism is an infantile disease. It is the measles of mankind." - Albert Einstein, The World As I See It

Seconding Prunus Girl. It is a shounen, but it's a cute romance too. I really enjoyed it and I don't normally like shounen. It's kind of debatable whether the character is trans or a cross dresser, though.

(I read Girl Friends but I don't remember any cross dressing in it?)

Also, the josei Kuragehime has the male lead dress as a woman most of the time. It's really good and light-hearted, so I think most fans of shoujo would like this one.

There is Shounen Oujo, which is a shoujo, though I have not read this one yet.

Hachimitsu Scans does a lot of series with men dressing as women. You can look through their series if you like and see if any interest you. They scanlate Kuragehime and Shounen Oujo.

Thanks for all the recommendations! 😀
I'll check them all out and thanks for the advice and help too, (with the filters and that)

Princess Princess
Usotsuki Lily
And uh, well, the guy is kinda girly Mizutama Honey Boy

Coda is the only shoujo with a male crossdressing/gender bender theme that I personally know of to recommend that I don't see being mentioned yet.

Himitsu no Himegimi Uwasa no Ouji

Summary:

Roochen and Galnia are two countries that have been at war with each other for a long time. Now that peace has been established, princess Aldina of Roochen has to marry the prince of Galnia. However, according to the rumors, the prince of Galnia is a total debauch, and he does nothing but playing around?! Aldina wants to see for herself who the prince really is, so she disguised herself as a boy and tried to approach the prince...