As a replacement for any resistance workout, 20 second reps are an excellent way to train.  Using these slow controlled movements, you can focus on technique and isolation of muscles.

Simply count to 10 while lifting and then again count to 10 as you lower the weight.

Your should not fully extend nor contract (bend) the muscles you are working. 

By the time you get to the number 10, you should have reached 80% movement.

Begin with 3-5 repetitions and increase as neccesary.