This tutorial shows how to make a signature with a writing tool.

You can save this one and open with your animation program to see what I did, if you get stumped. Or post a question on the message board.
The first thing you need to do is select your writing tool. You can use a pencil, pen, crayon, feather, or whatever you like. Next, calculate the approximate number of frames you will need. There should be about three frames per letter, plus one or two for your completed signature at the end, depending on whether you want to lay your tool down as I have done. Frames can be added or deleted as needed.
I find it is much easier to start with last frame first. It is also easier to use copy and paste, for each frame of your text. This way you only have to write your text once, and it will be in the same position in each frame.
Go to the last frame, after you have added all the frames that you think you will need.

Add your text to the last frame. Click the T (text tool), then click where ever you want your text to go.

The text entry box will pop up and you can type your text into it and choose your options (font, size, color, etc).

Then highlight your writing tool, so it is in the last frame with your text.

Position your pen (or whatever) over the last letter, as if you are just finishing up writing the name. Click on the pick tool and then just click your writing tool and drag it to wherever you want it.

You may need to adjust the canvas size so that it will be big enough for the writing tool to fit when it’s on the top part of your highest letter. Click Edit and choose Canvas size.

Highlight your text, at the right. Just click on it. Click Object and choose Convert to Image. You will only have to convert to image once.

Click Edit and choose Copy.
Go to the previous frame (just click on it). Click Edit and choose Paste. Highlight your writing tool, so it appears in this frame. Position your writing tool so it looks like you are almost finished writing the last letter of your text.
Highlight your text. Click the eraser tool.

Erase the part of your last letter you have not written yet. Copy your text again, so you have less to erase next time. Paste to the previous frame. Highlight your writing tool again, and position it. Then erase the part you have not written yet. Repeat for each frame, erasing as you go, until you have no text left to erase. When your text is all erased, you want to end up in your first frame, so remember to add or delete frames as necessary.
To lay down your pen at the end, add one more frame after your last one. Copy/paste your pen to the last frame. If you just highlight the pen, instead of copy/paste, then the pen will rotate in all of your frames instead of just the last one. Use rotate tool to get the pen into the proper position.

Next you will need to adjust your timing. Highlight the frame or frames, at the bottom, that need to be adjusted. To highlight all frames at once, highlight the first frame (just click on it) and then hold down the shift key while clicking on the last frame. Then right click on any frame, choose frame properties, and adjust the number. If you want only one frame to slow down, such as the end frame, then just highlight that one, right click and choose frame properties.
Make the number higher if you want the frame to pause longer, lower if you want the frame to go by faster. Pick "smart" for removal method on all frames, to keep you from getting duplicates when you have a transparent background.
Click preview. If it looks good, save it now. Otherwise you can keep previewing and changing your signature until it is the way you want it. Then click File and Save as GIF File. If you want to edit it later, you can save it as a UGA File instead.
Enjoy!