Ask Mr. Smarty Plants

Prunus mexicana (Mexican plum) is native to Texas and to the area around Cherokee County, so it should do well in your garden.

Here are the Propagation Instructions for Prunus mexicana (Mexican plum) from our Native Plant Database:

"Propagation Material: Softwood Cuttings
Description: Prunus species may be rooted from dormant hardwood, softwood, semi-hardwood, or root cuttings. Semi-hardwood and softwood cuttings taken in summer root easiest. Seeds of P. mexicana require a period of after-ripening followed by cold stratification.
Seed Collection: Collect fruit when it is filled out, firm, and its ripe color. Clean seeds from pulp. Storage viability is maintained at 31-41 degrees. Loses viability rapidly if allowed to dry out after collection and cleaning.
Seed Treatment: For spring sowing, stratify seeds in moist sand for 30-60 days in a greenhouse, then cold stratify (36-41 degrees) for 60-90 days. Plant well before high temperatures."

Sounds like you will be better off with the stratification method, rather than scarifying. Here is information from Suite 101 on How to Cold Stratify Seeds.

You cannot grow a new tree from a branch, but rather from cuttings of wood in various stages, as seen above in the Propagation instructions. For information on rooting cuttings, go to this North Carolina State University Extension website Plant Propagation by Stem Cuttings: Instructions for the Home Gardener. 

See this USDA Plant Profile on Prunus mexicana (Mexican plum) for pictures of the seeds.

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