I used a metronome, set to beat=2 (so alternating tones each tone being one of the 2 chords) , initially at its lowest speed (30bpm) increasing by 5bpm up to a target of 60bpm. When I felt like it I tried 70 or 80 bpm.

Usually ran for 2 minutes before upping by the 5bpm. Didnt increase unless felt reasonably ok

before going faster. Unless finding really easy resist temptation to increase by 10bpm, stick with 5.

Kept a log (spreadsheet) noting things , esp where it was wrong (eg "sometines muting x string on d chord" or whatever). Or any insights (e.g. "getting to A chord with time to spare but not E chord" )

A session of that maybe 15 miins allowing for making notes etc.

Experiment. One time I tried 8 minutes insted of the usual 2 & found got better after the 4th minute.

Hope that helps

Mike