your index and thumb, use the pick and your middle finger

4 Times (I)

e----------------------------------|
B----------------------------------|
G-----------4---2--1---------------|
D----------------------------------|
A--2-2------5---4--2---------------|
E--0-0-3-4----0--------------------|

2 times  (IV)

e----------5---3--2-------------------|
B-------------------------------------|
G----------5---4--2-------------------|
D-2-2--------0------------------------|
A-0-0-3-4-----------------------------|
E-------------------------------------|

Back to (I twice)then;

2 times  (V)

e--------------------------------------|
B-----------7----5--5------------------|
G--------------------------------------|
D--4-4------7----6--5------------------|
A--2-2-5-6-----------------------------|
E--------------7-----------------------|

Back to (IV twice) then (I twice) then the turnaround

e-----2-----|
B-----0-----|
G-----2-----|
D-----1-----|
A-0-1-2-----|
E-----------|

Then start the progression over again