There is no specific method for webcomic. I don't know about tutorial, but the basic steps are:
1. Rough draft of a chapter. You can do that anywhere as it doesn't matters much. 2. Draw the characters by using Photoshop (not compulsory) in a drawing tablet. 3. Artists prefer to draw backgrounds seperately in a 3D model function so that the characters can be placed in any location without having to draw background scene for different angles every time. 4. Coloring the panels. It also includes shadowing, etc... The time taken varies on your skill. 5. Placing word bubbles on panels.
There is no thing as a fix guide. Every artist has his own style. Many artists reveal their work style in extra chapters.
You will need editing program like Photoshop CSS, which does raster as well as vector (basically has functions of the older versions of Illustrator and Photoshop into one program) also really helps to have a tablet (I have a Wacom and recommend it, I think they might still come with Essentials (Adobe) which is like a scaled down version of Photoshop, but still gets the job done for drawing/digital painting etc.
Few more helpful hints, Screentones, stamps, patterns can be really useful for backgrounds, effects, etc. There are a bunch on this site, including image packs and the link (although these are generally if you want to look more like traditional manga, but can also be useful for color/webtoon too):