Understanding Society User Support

Hello,
I was wondering if some R sample code may be available for longitudinal weighting. I am merging variables from w_indresp and w_child, each with different weight variables, then analysing trends across 4 waves. The in-wave files are merged by hidp and selected for w_rapno8 (adult responding to breastfeeding questions).
I am assuming I must weight the data within its original file before merging.

For example,
in j_child, the weight I need is j_psnenui_lw.
and in j_indresp: j_indscui_lw.

Many thanks for any advice.