You are correct that PROPWT does not generate population-level estimates; it inflates to the number of valid diary entries. My previous response will be edited to ensure that accurate information is given to future readers of this post. OCOMBWT is the appropriate weight to use in order to get national population estimates. According to the description tab for OCOMBWT, “If the original weight is inflated, OCOMBWT is left inflated”. It is important to consider that there are comparability issues with OCOMBWT because it inflates samples differently based on the original survey and because the specific target population will vary by sample. Also, keep in mind that this weight may include “bad” diaries if the original weight did not exclude them.
As a sanity check, I created extracts using both ATUS and MTUS in 2018 to compare population estimates using WT06 in ATUS and OCOMBWT in MTUS; they provide matching population estimates. You can find more information on specific samples from the MTUS source documents page, and may be interested in the weighting-specific information in the MTUS Coding Procedures document from the IPUMS Time Use team’s colleagues at the Centre for Time Use Research.