The IERS Technical Note 2010 for the Effect of solid Earth tides on the Geopotential (chapter 6.2) recommends a 4 step approach:

1) frequency independent part

2) frequency dependent corrections

3) remove permanent tide

4) add pole tide

Step 1 is quite straightforward, while step 2 is more complex and computationally intensive. It is not clear to me whether Step 3 and 4 make sense without step 2.

How good is the approximation (percentage of total effect) if only step 1 is implemented?