The Tigers have agreed a reported £2million fee with SC Paderborn for Proschwitz, 25, who has agreed a three-year deal and had his medical at the KC Stadium on Tuesday.
Hull manager Steve Bruce is also hoping to conclude a deal for former West Ham defender Abdoulaye Faye "in the next 24 to 48 hours" after holding talks with the 34-year-old.
The former Senegal international, who has previously played for Bolton, Newcastle and Stoke in the Barclays Premier League, made 29 appearances for the Hammers last season before being released earlier this summer.
Meanwhile, Bruce's son Alex started for Hull in Tuesday night's 5-0 friendly win over Winterton Rangers.
The 27-year-old defender was released by Leeds after being restricted to eight first-team appearances at Elland Road last season.