Before doing anything else you need to modify your .vimrc or _vimrc (under Windows) file to detect XRC files as a separate file type. For this simply add the following line to it:
au BufNewFile,BufReadPost *.xrc set ft=xrc
I also like to start with XML boilerplate already filled in when I create a new file so I additionally have
au BufNewFile *.xrc read ~/vim/template.xrc
where the file template.xrc contains
<object class="" name="">
Now, I'd like to do spell checking in the XRC elements which contain user visible text. For this I create the file ~/vim/syntax/xrc.vim (this works under Windows too, just use whatever Vim considers to be your home directory instead of ~) with the following contents:
syn region xmlString start="\(<title>\)\@<=[A-Z0-9]" end="\(</title>\)\@=" contains=xmlEntity,@Spell
syn region xmlString start="\(<text>\)\@<=[A-Z0-9]" end="\(</text>\)\@=" contains=xmlEntity,@Spell
syn region xmlString start="\(<label>\n\?\)\@<=[A-Z0-9]" end="\(</label>\)\@=" contains=xmlEntity,@Spell
and enjoy Vim help with correcting your mipsellings (how did you notice I wasn't writing this post in Vim?). Notice that the region definition is not very elegant but this was the best way I could find to make it work: using \zs unfortunately didn't work.
Next, I also defined a couple of helpful macros to insert the common constructions into XRC. This is done in ~/vim/ftplugin/xrc.vim (which will be sourced automatically by Vim thanks to our file type autocommand):
nmap <Leader>o o<object class=""><C-M><Esc>kf"a
nmap <Leader>v o<object class="wxBoxSizer"><C-M><Esc>O<Tab><orient>wxVERTICAL<Esc>o
nmap <Leader>h o<object class="wxBoxSizer"><C-M><Esc>O<Tab><orient>wxHORIZONTAL<Esc>o
nmap <Leader>i o<object class="sizeritem"><C-M><Esc>O<Tab><flag>wxALL<Esc>o<border>5
Notice that this supposes that you have the XML editing plugin installed, notably it relies on it to close all the tags. But surely you don't edit XML in Vim without it anyhow, right?
Much more could probably be done but I find that the above already makes editing XRC much more comfortable. And I definitely can do it much faster in Vim than using any GUI I tried so far.