Howdy Senior C
Here is the link for forms
http://www.trec.state.tx.us/Most of the time you will use the 1 to 4 family resale form, You can get them at title companies etc. To assign your contract all you need is a one paragraph agreement between you and your buyer stating the amount you will get paid and the earnest money to be put up and your buyers agreement to close on your contract. Title companies sometimes have some forms available for this too. Find a closing offer that is familar with flips and wholesale deals. A lot of them do this stuff everyday and for years.
The short list is to find a good deal and find a buyer for it that is qualified to do the deal. Start the title search as soon as you get the thing under contract. Some Realtors may have even done this for you already, a service some title company offers some Realty companies. Having a good mortgage broker is important too, one that works investor deals and even gard money lenders. Your buyer may already have this but it could be helpful to have one just in case.
Knowing the resell value and the rehab costs would be helpful and here again the buyer will want to form their own opinion and costs breakdowns but it helps to be able to say what the costs will be and what you can sell it for and what your profit range could be.
Hope this helps some