Both Chan and Tantric methods referred in the Huayen practice are Huayen Chan and Huayen Tantric.

For Huayen Chan, please go to the Huayen Quarterly Journal section of this
website, look under Spring 2007 issue and you will find the article
"Huayen Chan" . That article will give you a detail elaboration
of HY Chan.

Based on the theory, state of mind and principal of
Huayen School, Huayen Tantric is an intrepretation of a complete
structure of tantric practice, as well as the manifestation that will
be attained. It embraces the Tang Tantric, which is the Esoteric Buddhism
brought in from India during the Tang Dynasty.

HY Tantric is distinct from the Japanese Tantric or Zhenyan/Shingon and the Tibetan Tantric.

TLC

[It embraces the Tang Tantric, which is the Esoteric Buddhism
brought in from India during the Tang Dynasty.

HY Tantric is distinct from the Japanese Tantric or Zhenyan/Shingon and the Tibetan Tantric. ]

Shingon tantra, as far as I know, has been based on three main sutras:

-Mahavairochana sutra/Taji ching/Dainichi kyou/Sutra about the Great Sun

-Vajrasekhara sutra/Chinkangting ching/kongouchou kyou/Sutra about the diamond crown

-Susiddhikara sutra/Su-hsi-ti ching/Soshitsuji kyou/Sutra about achieving perfection

which were brought to China during Tang epoch and on commentaries by Dharma teachers such as Shan Wu-wei(Subhakarasimha), Pu-k'ung(Amoghavajra), I-hsing, Chin Gang-chi(Vajrabodhi), Pan-jo(Prajna) and others. 

Have these sutras and these teachers played role also in Huayen tantra?

Besides Shingon, I have come upon a school of Korean tantra called Jingak.

http://www.jingak.or.kr/main.asp

Unfortunately it is only in Korean. Maybe you know something about it.

華嚴密法簡介

中國密教的演變：

早期密教是指密宗兩部根本經典（大日經與金剛頂經）未結集流傳前，由釋迦牟尼佛顯說於佛教經典各部中的密法及陀羅尼密咒等。

中期密教是指由法佛大日如來所傳密宗，「胎藏界」、「金剛界」兩部大法，以及兩部根本經典「大日經」、「金剛頂經」結集傳出後之密教。具體地說，就是由開元三大士（善無畏、金剛智、不空）所傳的密法—由中國僧人一行、惠果繼傳而發揚的「唐密」，以及由日本僧人空海、最澄繼承唐密而在日本創新發展的「東密」和「台密」。

後期密教是指印度那爛陀寺及超戒寺後期發展起來的「金剛乘」、「時輪乘」的密教。它由蓮花生等上師傳至中國西藏，成為藏語系佛教，即藏傳佛教中的「藏密」。

華嚴密法：

華嚴密法是以華嚴宗的理論、境界來詮釋密法整個修行的架構，以及所要成就的世界；它包含一般所稱的唐密。

它是由印度開元三大士傳入唐朝，融合中國思想文化所發展出來的密法。它是「金胎合曼」的佛陀境界，也是華嚴海印三昧的修法，理論與行法都相當完備的體系。

華嚴密法的特色：

胎藏界與金剛界兩大法在印度是各自分開傳的。這兩部大法傳入唐朝後，經「金善互授」（金剛智、善無畏）兩部大法互相交流，結集而成為「金胎合曼」一部完整的密法。

華嚴密法與藏密、東密有何不同：

藏密是指後期密教，由阿底峽尊者傳至中國西藏，後經蓮花生大士復興，融合西藏文化，發展至今的「寧瑪派紅教」、「薩迦派花教」、「噶舉派白教」、「格魯派黃教」及原有苯教發展的黑教等多種教派。

東密、台密是日本僧人「空海、最澄」繼承唐朝的唐密、天台密而傳至日本創新發展的密法。它們融合日本文化，僅保留了金剛界、胎藏界的理論、行法，並未發展出「金胎合曼」的體系。

Dear Linas:

I hope that you understand Chinese. If not
it will take us a while for these materials to be translated into
English. Please let me know if you like/need this to be
translated.

Dear TLC,

I read some writen Chinese although I am not yet fluent reader(and absolutely cannot understand o speak spoken Chinese). I was able to understand the gist of what you posted, and as far as I understand the most inportant distinction between Huayen Tantra and Shingon is that while the former uses combined Vajra, Womb mandala(金胎合曼), the latter uses two separate Vajra and Womb mandalas.

I have another article in Chinese concerning Tang period Tantric Buddhism where I have found some additional information.

http://www.china.com.cn/chinese/zhuanti/fzslfggf/573206.htm

Thabk you for your help。謝謝您。