I don't know if this is general knowledge but here is my way of doing time stretching with Orion's DrumRack:
1. Load the sample into a track of DrumRack.
2. Activate the CUT TRK parameter of this track.
3. Fill the WHOLE pattern with 16th, 32th or shorter notes.
4. Automate the OFFSET parameter.
5. Play around with it.
I know, this is not very professional but it works well for many time stretching tasks.
EDIT: Damn! I've been using this technique for more than three years. After I have written this forum post, I thought about it again and figured out, that time stretching can be realized more comfortable with Orion's Sampler (using START parameter instead of OFFSET) .