what were the two attacks huston used to overturn plessy vs ferguson?

Answer 1

Plessy v. Ferguson was overturned by Brown v Board of Education in 1954. Unfortunately, Huston died of a heart attack in 1950.

Charles Hamilton Huston started the fight to overturn Plessy, along with Thurgood Marshall, with the case of Murray v. Maryland in 1936.
Murray v. Maryland, 169 Md. 478 [Segregation]
1937, Baltimore, Maryland

The other key case from this period was Missouri ex rel.Gaines v. Canada, involving Lloyd L Gaines, who wanted to attend the University of Missouri (1938).
http://www.brownat50.org/brownCases/PreBrownCases/GainesvCanada1938.htm

Case related to Plessy and Brown:
http://brownat50.org/brownCases/BrownCasesFrameset.html

Answer 2

Charles Hamilton Huston, vice dean of Howard Law School, had a plan. He believed that training black lawyers and sending them south to work was the first step in abolishing segregation. “Experience has proved that the average white lawyer, especially in the South, cannot be relied upon to wage an uncompromising fight for equal rights for negroes,” Huston declared.

As special counsel to NAACP in 1935, Huston began a legal campaign to end segregation in public schools. His strategy included documenting the inequity between educational opportunities for blacks and whites and reinforcing the expensive price tag associated with separate and equal schools. He believed a broken “separate but equal” policy would eventually eliminate discrimination.